Look around the top of politics and it seems like a wonderful time to be a woman. Two of the four candidates for the Labour leadership are female – Yvette Cooper and Liz Kendall – as are three of the five in the race for deputy: Stella Creasy, Caroline Flint and Angela Eagle. One of the three likely contenders for the next Tory leadership is a woman, Theresa May. The next leader of Scottish Labour is likely to be Kezia Dugdale, and she will find herself debating two other female leaders, Nicola Sturgeon of the SNP and the Tories’ Ruth Davidson. Half of the shadow cabinet is female, and there are seven women in the cabinet. The most powerful politician in the European Union and perhaps the world is Angela Merkel.

But these eye-catching facts conceal an uncomfortable truth: remarkably high proportions of the most successful women in politics are childless. (All the named politicians above are, except Cooper and Flint.)

For much of the last parliament, the only mother in the cabinet was Maria Miller, and New Statesman research shows that while the 14 men in the shadow cabinet have 31 children between them, the 13 women have only 16. Seven of the women are childless, against three of the men.

This disparity is evident throughout parliament, according to wider research carried out by the academics Sarah Childs and Rosie Campbell in 2013. They found that 45 per cent of female MPs were childless, compared to 28 per cent of men. “On average men MPs have 1.9 children compared to 1.2 for women MPs,” they wrote. “There is also a sex difference in the age of MPs’ children: the average age of MPs’ eldest child when they first entered parliament is 12 years old for men and 16 years old for women . . . All of this would suggest that mothers – and not just women – are significantly descriptively under-represented in British politics.”

Why does that matter? It matters not only because a parliamentary democracy should strive to reflect the populace it serves, but because the barriers stopping the ascent of MPs who are mothers reflect the structural discrimination throughout society.

The “motherhood trap” exposes one of capitalism’s most uncomfortable secrets – the way it relies on so much unpaid labour, often from women, to sustain itself. This labour comes at the expense of career opportunities, and their lifetime earning power: the pay gap between men and women in their twenties is all but eradicated, but a “maternity gap” still exists, and women’s wages never recover from the time devoted to childbearing.

Despite this, and despite the huge energy generated by the feminist movement in the past decade, questions of care have not gained as much attention as they did during the “Second Wave” in the 1970s. In 2014, the New Republic’s Judith Shulevitz suggested that the F-word itself should be replaced with “caregiverism”, to stress that challenging the exploitation of unpaid labour was critical to achieving equality. Without a structural analysis of the problem, Shulevitz argued, it was too easy to see these debates as “personal dilemmas – opting out, opting in – rather than as Hobson’s choices imposed on us”. She added: “Limiting work hours used to be one of the great causes of the labour movement.”

That brings us back to parliament. Over the past month, I have spoken to more than a dozen women and men, many of them involved in politics at the highest levels. There was universal agreement across the ideological spectrum that it is difficult to balance caring responsibilities with a political career. At the same time, selectors, voters and the media often expect a politician to have a family as a way of signalling that they are “normal”. So women face an impossible situation. If they have children, people disparage them as not dedicated enough to the job. If they don’t, people disparage them for having nothing else in their lives but the job.

Indeed, a 2014 study found that when it came to workers having children, there was a “fatherhood bonus” but a “motherhood penalty”. As the author of the study, the sociology professor Michelle Budig of the University of Massachusetts, Amherst, told the New York Times: “Employers read fathers as more stable and committed to their work; they have a family to provide for, so they’re less likely to be flaky. That is the opposite of how parenthood by women is interpreted by employers. The conventional story is they work less and they’re more distractible when on the job.”

Rosie Campbell and Sarah Childs think the same is true of MPs. “It’s a no-win for women,” Campbell told me. “For men, having a wife and children is a political resource, whereas for women, not having children was the thing that gave them the time to do politics.”

The downside to this added time, however, is being open to accusations of selfishness, and the suggestion that the women have made a calculated career decision that somehow alienates them from “ordinary people”. (Roughly 20 per cent of women in the UK aged 45 do not have any children, according to the Office for National Statistics, up from one in nine of their mothers’ generation: not having children is far from rare.)

On 6 July in a column for the Huffington Post, the former Labour minister Helen Goodman wrote that she supported Yvette Cooper for leader because, “As a working mum, she understands the pressures on modern family life. We need a leader who knows what challenges ordinary people face day to day, and who is committed to helping them.” The implicit contrast here was with Liz Kendall, who is both childless and single, her last relationship having ended just before the general election.

But as Isabel Hardman wrote in a blog for the Spectator, “Being a parent does not automatically mean you will understand even other parents. You will still need empathy in order to put yourself in the shoes of a single mother living on benefits if you are married and running a house on two salaries.” In other words, Cooper and Kendall have more in common with each other, uterine usage aside, than either does with a constituent struggling on the minimum wage.

Yet speaking “as a mother” is presumed to be a short cut to authenticity and normality. When Maria Miller wanted to bring in controls on web access to hardcore pornography in 2013, she told the press: “As a mother, I am determined to protect my children from the depravity of internet porn.”

Male politicians, by contrast, get the best of both worlds. They have a family that can be marshalled as photogenic props or used as fodder for personal anecdotes in speeches, and their home life grounds them and makes them appear “normal”. (The coverage of the Cooper/Kendall spat largely failed to mention that Andy Burnham and Jeremy Corbyn have children. And most commentators presumed Miller’s comments to be a coded gibe at Theresa May, Theresa Villiers and Justine Greening but not Eric Pickles or William Hague.)

So, what can be done to make life easier for both sets of women – those caught in the motherhood trap, and their childless sisters, portrayed as selfish and single-minded? Just as importantly, what can be done to bridge the gap so that a woman’s family status is no longer seen to define her quite so acutely? Let’s look at each in turn.

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In May 1997 a record 101 female Labour MPs entered the Commons. It was parliament’s own version of the Big Bang, driving up the percentage of women in the House from less than 10 to more than 15 per cent. There was strength in numbers, allowing policy areas that had been marginalised – or dismissed as merely “women’s issues” – to be heard. The macho, public school-cum-gentleman’s club culture of Westminster also took a knock. But there was a problem. “Lots of us who were newly elected in 1997 came in assuming it was fine – we were ­going to sort out the hours of the House of Commons,” the former Labour minister Patricia Hewitt told me. “And we assumed that all female MPs would have the same view on this.”

They didn’t. Politicians who lived within commuting distance of London, or whose family home was in the capital, wanted parliament to operate to normal working hours so that they could get home in the evenings to see their children during the week. But Hewitt and her colleagues discovered that MPs in farther-flung seats were away from their family during the week anyway, and so didn’t mind the long sitting hours. They wanted a late start on Monday and an early finish on Thursday to maximise the time they could spend with their family.

They also discovered that many male MPs liked the late sittings and the “collegiality” of the Commons. Hewitt recalls: “Many of them would make the argument: ‘No, no, no, it’s absolutely vital that we’re voting in the evening, we’re having dinner together. That’s when back benches can talk to ministers.’ And there was a lot of truth in that; it was just you also pay a high price for it. So that was quite a rude awakening.”

The current standard sitting hours run from 2.30pm to 10pm on Monday, 7pm on Tuesday and Wednesday, and 5pm on a Thursday. At these times, MPs are expected to stay near Westminster in case they need to vote. This part of the job, coupled with the need for most MPs to maintain two homes, is the great barrier for those with caring responsibilities.

Many believe that discussions over sitting hours operate as a veiled rebuke to women who don’t seem to want to be part of the (male) clique. “It’s interesting that very often the criticism of women is that they’re not ‘clubbable’,” says Emily Thornberry, the Labour MP for Islington South. “Theresa May ‘doesn’t have a following’; Yvette Cooper is ‘too reserved’.” Another MP, who is also a mother, echoed this: “If we had an early finish, my priority would be to get back and spend time with my family. Even before I had a child – it’s just a question of personal choice – sometimes I’d just rather read for a couple of hours.”

Labour’s women’s minister, Gloria De Piero, says she does not believe it is possible to “tinker” with the hours any more to make them more family-friendly. But she added, “You’d have to say: ‘If you invented it now, is this what it would look like?’”

However, other aspects of Commons life are improving. There is now a crèche on Parliament Street, used by MPs, civil servants and staff, which takes children from three months upwards. It was created by Speaker John Bercow in 2010 amid a campaign of low-level resistance, because its establishment led to the closure of Bellamy’s, one of the many bars in the Commons.

Bercow has taken reform seriously as Speaker, and he told me by email: “A good number of the old, outdated assumptions about women’s ability to be effective Members of Parliament and hold high office have been consigned, rightly, to the dustbin. However, as with other highly mobile careers, it is a fact that an MP’s job, often splitting time between his or her constituency and Westminster, places a particular strain on family life.” Besides the crèche, he says, “the decision to introduce earlier sitting hours in the last parliament was undertaken partly as a result of colleagues arguing that a modern Commons should take a more family-friendly approach”.

The current sitting hours are, however, in danger, as they were introduced for a ­limited period and some MPs will want them back to their old length. “I don’t think reverting to those hours would send a good signal about modern working practices,” one female MP tells me.

Still, at least you can now take a baby through the division lobby, making it easier for those with small children to attend crucial votes. This milestone was first reached by the Liberal Democrat MP Duncan Hames in 2014 when his wife, Jo Swinson, was the party’s equalities minister. She told me that her family provided a perfect test case for people’s differing responses to mothers and fathers juggling work and childcare.

“Duncan and I had the same job as MPs, and I had ministerial responsibilities, but people still responded differently in terms of expectations of what childcare responsibilities we would have. People just took it for granted that with a small child, there would be times when I, as a woman, couldn’t do something. But they didn’t respond in that automatic way to Duncan at all.”

Swinson argued that childcare affects working fathers in a way that doesn’t get addressed “because they’re not physically going through that change”. She added: “I think fatherhood is much more invisible in politics. The media is part of it – the woman will be introduced with what age they are, ‘mother of X’; or, indeed, if they don’t have children, then it will be remarked upon in a way that it isn’t with men, generally.”

She also highlighted the difficulty of ­taking maternity leave as an MP: her office covered her constituency caseload while her Lib Dem colleague Jenny Willott took on the equalities brief in addition to her own. Swinson believes that Britain should move towards the Scandinavian model, under which a portion of paid parental leave is available only if taken by the father (or same-sex partner). “Because of maternity leave, and the cultural expectation that it’s mums that take the lion’s share of that time,” she said, “it ends up being the women who are taking more of the responsibility once they return to work.” Why is that? “Because they’ve developed the expertise. Parenting is about practice – you don’t innately know how to calm a crying baby.”

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One of the hazards of my job is being invited to summits on “powerful women”, which usually leave me feeling extremely unpowerful, and frankly a bit of a failure at being a woman. Recently at one such occasion, held in the ballroom of a London hotel, the star guest was the former Australian prime minister Julia Gillard. She talked frankly about what has become known as the “misogyny speech” – when she took her main opponent Tony Abbott to task in parliament for 15 searing minutes, opening with the declaration: “I will not be lectured on sexism and misogyny by this man; I will not.”

The denunciation, in October 2012, had been a long time coming. Even judging by the everyday tone in the notoriously brutal arena of Australian politics – its bluntness often makes Prime Minister’s Questions look like a Quaker meeting – the rhetoric used to describe Gillard was exceptionally vicious. “Ditch the witch”, read one set of election placards. After her speech, the sexist abuse did not abate: in 2013 a Liberal Party fundraising dinner promised “Julia Gillard Kentucky Fried Quail – Small Breasts, Huge Thighs & A Big Red Box”. (Abbott said the menu was “tacky and scatological” but he did not suspend the candidate involved.)

Through this river of low-grade sexism ran one very strong current: repeated criticism of Gillard for being childless. In 2007, the conservative senator Bill Heffernan called her “deliberately barren”. Another Liberal politician, George Brandis, now attorney general, once criticised her in parliament, asserting that she was a “one-dimensional” person who had “chosen not to be a parent”. Her own party has not spared her: the former Labor leader Mark Latham opined in 2011, “Anyone who chooses a life without children, as Gillard has, cannot have much love in them.” Her fierce rival Kevin Rudd, the former prime minister, is alleged to have described her pejoratively, also in 2011, as a “childless, atheist ex-communist”. In February the following year, the Sydney Morning Herald fretted in its leader column that voters had “largely closed their minds to Gillard. Her media persona does not fit the expectations of some voters: a single woman, childless, whose life is dedicated to her career.”

As often seems to be the case, it was implied that given Gillard’s childlessness, she could not have an opinion on family policy – as if defence ministers always have a military background, or all agriculture ministers can reliably tell one end of a haddock from the other before taking on the brief.

A fortnight after the misogyny speech, Tony Abbott made a pointed remark about Gillard’s government restricting the “baby bonus” for new parents on the assumption that a second child could reuse many items purchased for the first. “Often one child is still in the cot when the second one comes along. One child is still in the pram when the second one comes along,” said the father-of-three. “I think if the government was a bit more experienced in this area they wouldn’t come out with glib lines like that.”

The Conservative children’s minister Tim Loughton took a similar line when criticising his Lib Dem coalition colleague Sarah Teather at the Tory party conference in 2013, claiming that she “didn’t believe in family. She certainly didn’t produce one of her own.” This made the Education Department a “family-free zone”, which he found “disappointing”. (Loughton has three children, although it would be indelicate of me to note that his contribution to “producing” them involved less physical hardship than endured by his wife.)

Perhaps the most startling aspect of Julia Gillard’s experience is that the criticism of her was so explicit and came from such senior political figures. In less plain-spoken cultures, the fear of childless women is usually better camouflaged, disguised as concerns over “life experience” and whether a woman has a “well-rounded personality”. But not always: in June last year, a 35-year-old Tokyo City assembly member called Ayaka Shiomura was heckled during a debate on support for working mothers with cries of “Go and get married” and “Can’t you give birth?”. In 2005, when Angela Merkel first seemed to have a chance of leading Germany’s ruling coalition, the wife of her main rival, Gerhard Schröder, commented acidly that she “does not embody with her biography the experiences of most women”, going on to mention childbirth and school admissions. That Doris Schröder-Köpf’s own husband has no biological children – the couple have adopted two children, and she brought a daughter to the relationship – did not seem to trouble her.

The childless British politicians to whom I spoke confirmed that their status was often used against them by their opponents, by other women as much as men. One pointed me to the leaflet issued by Stella Creasy’s Tory rival for the Walthamstow seat in this year’s general election, Molly Samuel-Leport. Under the headline “The Contenders Head to Head”, it listed Samuel-Leport’s virtues: “Cleaner Mother Shop Assistant Wife Athlete Teacher Champion Understands YOU”. When it came to Creasy, the list was shorter: “Career Politician Understands Ed Miliband”. The implication was clear – Creasy’s childlessness showed that she was not an “ordinary” person, as did her a PhD in social psychology and her background in think tanks.

Similar criticisms were levelled against Theresa May by a Downing Street insider in the Daily Mirror in August 2014 just as she became the front-runner to succeed David Cameron. May has always been reluctant to talk about not having children; the most she has ever said is that it “just didn’t happen” for her and her husband, Philip.

The source said that May’s lack of a family would make her look abnormal and unappealing to the electorate. “Being interested in politics is not normal. It’s not something most people do,” the source told the paper. “There are lots of ways you can look like you are obsessed with politics and not having children is one of them.” (Let’s draw a veil over what her rival Boris Johnson’s ­fertility track record makes it look like he is obsessed with . . .)

Do male politicians feel such criticisms as strongly? Ben Bradshaw, who is also in the race for the Labour deputy leadership, told me he had never been aware of his childlessness being used as a political attack line.

“It’s never been raised with me – that idea that because you don’t have children you don’t understand people’s lives,” the 54-year-old MP said. “We all have families even if we don’t have children. Me and the man I’ve been with for 20 years have an extended family. We have scores of nephews and nieces.”

Nicola Sturgeon has said that she believes there is a double standard. Asked on ITV’s Tonight during the general election campaign about whether she had chosen not to have children, she said: “Alex Salmond doesn’t have children. He might tell you differently, but I’m not aware of reading an interview or seeing an interview with Alex Salmond asking that question.”

Gloria De Piero, who is married but does not have children, says this reflects her experience. “It is mentioned in a lot of interviews with me in a way that it just simply isn’t with my male colleagues who are similar ages,” the 42-year-old told me. “It’s an issue for women who are not mothers in a way that it’s not an issue for men who are not fathers.”

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The motherhood trap affects us all, and although some of these issues are specific to MPs, many are not, particularly the scourge of “presenteeism” – rewarding attendance, whether productive work is being done or not – and the valorisation of “unencumbered” workers, who are available to their employers at any time of day or night.

Yet the politicians I interviewed were keen to stress that there are still grounds for optimism. “I don’t want to be too miserable about this,” said De Piero, laughing. “I always worry that people say, ‘It’s so bloody awful in parliament,’ and women go, ‘Oh my God, I don’t want to do that job.’”

Several parliamentarians also had ideas for how working practices could be improved. Emily Thornberry questioned why there was a need for the House to return to sit before the autumn party conferences, even though at this time, little useful work is done on legislation. Instead, she advocates a longer summer recess, during which MPs can have time off with their family, followed by a “constituency month” to catch up on casework. “They talk about ‘MPs have packed their buckets and spades and are off and we won’t see them’. We don’t stand up for ourselves and say: ‘I get 1,000 letters and emails a week.’ I have a lot of work to do in my constituency.”

The president of the Liberal Democrats, Sal Brinton, thinks it is time to talk seriously about job shares for MPs. “[It] frightens parliamentarians, but we think it’s something that would bear looking at. It used to frighten big companies, the idea that you could have a senior manager job-sharing, but it does work. You just have to think out the difficult issues – how do you vote? – but everything else would work.”

Jo Swinson also believes that the lack of maternity cover could be resolved with electoral reform. “It’s difficult with first-past-the-post, but in countries with list systems, people can do cover for certain amounts of time.”

Perhaps as a first step it would be easier to let ministers job-share. Patricia Hewitt says she suggested this in 2001, when Tony Blair appointed her to the cabinet, in a push to get the junior minister she wanted.“The one I had my eye on was doing a fabulous job in a different department. It was very funny, because Tony said, ‘Er, what’s that?’ Jonathan Powell [Blair’s chief of staff] was standing there saying, ‘Two people sharing one job.’ Tony said: ‘Are we allowed to do that?’ and Jonathan said: ‘Well, I don’t know. I’d have to check.’”

Unfortunately, the minister involved got another job and the point was never settled. Hewitt acknowledges that the sharers would have to be compatible – “the nightmare would be . . . a woman with some children and an ambitious man” – but she points out that job-sharing is now common in the public sector and charities.

The final, and most contentious, point is money. During my conversations, the name “Caroline Spelman” frequently crept into the discussion: an example of someone whose childcare arrangements attracted criticism and unwelcome press attention.

In 2009 the former Conservative chair had to repay £9,600 in expenses after Commons authorities ruled that she had been paying her nanny from public funds by employing her as a secretary. Three years later, Spelman lost an attempt to stop the Daily Star Sunday reporting that her 17-year-old son, who played rugby for England under-16s, had taken banned substances after suffering a sports injury. “It’s hard to know you’re putting your children in the public eye like that,” one woman told me. “There’s something about a mother’s hormones.”

Although very few MPs are willing to go on the record, many believe that the reforms to expenses – necessitated by wide-scale fraud and the overclaiming endemic in parliament before 2009 – have made it much harder for those who are not already wealthy to juggle the demands of work with family. The current system makes it far easier for the rich and unencumbered. “You hear that MPs should be treated as ordinary people,” one told me. “That’s nonsense. It’s a unique set of challenges. Ninety per cent of us work in two places. There’s an extraordinary rate of failed marriages.”

The wife of another MPs talks about “eating crisps and crying at home” in the early days of her partner’s career because he was so rarely around to help with the children. Several mentioned that it was a huge advantage to have a seat in London, which allows the MP to get home every night.

By way of a solution, the Conservative backbencher Charles Walker has proposed that MPs’ expenses be abolished and a fixed annual stipend introduced. Their claims for tax-deductible items would then be regulated by HM Revenue & Customs, just like for any other self-employed worker. “You can change the hours but it’s not going to help someone get home to Cumberland,” he added. “And there’s a ridiculous belief that MPs only work when the House is sitting.”

On the other side of the fence, most agree that the big battle for childless MPs is perception – often in the media, rather than among voters. Ben Bradshaw says he believes his constituents “don’t give a hoot” about whether or not he has children. Some worry whether selection panels – which are not allowed to ask directly about candidates’ children – kibosh women for fear that voters won’t like them, or that they won’t have time to do the job properly. “I was asked in 1998 by a woman councillor when I went for selection how my children were going to cope, and could my husband cook the dinner when I was out canvassing?” says Sal Brinton. “Where do people get these ideas from? That’s the bigger problem: perception, rather than the reality.”

Childless women, on the other hand, face greater problems later on in their career when going for leadership roles, as they are deemed to lack the “complete package” that voters want. Several of the women I interviewed said they thought that starting a parliamentary career in your twenties or early thirties made having a family harder. “I think what happens is that women find it difficult to establish themselves in those careers. And to get promoted. So they put off marriage and children and whatever, and often end up running out of time,” says the Labour MEP Mary Honeyball. Another source told me that single women who entered parliament often found it hard to meet a partner prepared to join “the Denis club” – a reference to the sacrifices Denis Thatcher made to support his wife’s ambitions.

In the end, what both mothers and non-mothers need is broader social change. First, there must be an end to a culture that sees childlessness in women as selfish, and their lives as inevitably emotionally stunted and unfulfilling. We need to reset our relationship with work – to resist the pressure of presenteeism and expectations of unpaid overtime, and to fight for better labour rights, as well as employment protection for those with caring responsibilities. As Ben Bradshaw, who looked after his mother in his teens when she was diagnosed with Alzheimer’s, puts it: “The more insecure people are in work, the more difficult it is for them to make choices around caring.”

Our parliamentarians’ job insecurity is rather different from that of someone on a zero-hours contract, but both would benefit from a reappraisal of what it is reasonable for employers to ask of their employees. Until then, men enjoy a double advantage, whether they have children or not.