Stella Creasy is fascinated by how things work – the texture of politics; its levers and logjams. At a cafe in her constituency of Walthamstow, she whips out her iPad to show me the bespoke software she uses to record her constituents’ interests and concerns. It’s a step forward from the standard Labour voter database, Contact Creator (although, thanks to its continental developers, quite a few of the instructions are in French).

On the day we meet, a LabourList poll has just suggested that she might be in with a chance of winning Labour’s deputy leadership. This is significant for several reasons. First, it is a challenge to Tom Watson, videogame enthusiast and union favourite, who has led the race from the very start. Second, it is interesting for what it suggests about the mental calculations of Labour supporters. How many of them are voting for Jeremy Corbyn for leader, but feel they cannot pick another man for deputy? And how many anti-Corbynites are voting for a deputy they expect – perhaps even hope – will take over if the left-winger gets whacked by a shadow cabinet coup?

Creasy won’t be drawn on the Kremlinology, but confirms that she would be happy to be deputy to Corbyn, or any of the other candidates: “I’ve worked with all these people, because what I want to be is part of a Labour movement.” She praises the enthusiasm of his supporters, saying he taps into “people's sense that they want being involved in a political movement to mean more than leaflet rounds”.

She joined the Labour party in 1994, aged 17, because “I thought, I want things to be different”. After working in a think-tank and as a parliamentary researcher, she became MP for Walthamstow in 2010 and increased her majority substantially at the last election. She now asks herself whether she would join the Labour party again if she were transported back to her teens. One of the conclusions from this line of thought is that Labour needs to connect more with single-issue campaigns – she cites No More Page 3 – and other political movements, such as the Women’s Equality Party. But the latter plans to run candidates against Labour at the next election, I say. “I look at the Women's Equality Party and the challenge that they set about who's championing equality . . . it is a danger for us that people will find other outlets for engaging in progressive campaigning and policymaking and change.” When I suggest that Labour has been poor at capturing the recent energy of the feminist movement, she points out that there are constituency parties where only one in four members are women. “I am of that generation of feminists who dropped the ball, because we looked at the gains our mothers and fathers had made, and thought 'brilliant, we're on the road now', and somewhere along the way, not only did progress stall, it went backwards,” she says. Referring to George Galloway’s notorious remarks on Julian Assange, she adds: “So we're having debates again about whether rape can exist within relationships, it's ‘bad sexual etiquette’ apparently. It really is not.”

Creasy’s approach to feminism is distinct from other politicians of her generation because it is so uncompromising. She says that she was told that calling herself a feminist was “career suicide” and that she wants to scream when people ask if she was inspired by Margaret Thatcher. (“When I get asked that, mainly by men, I ask if Berlusconi inspires them.”)

It is hard to imagine her laughing off a question from an interviewer about her weight, as Liz Kendall did with a joking “fuck off” to the Mail on Sunday. At the end of the interview, I ask her two light-hearted questions: does she get the night bus, like Jeremy Corbyn? And where does she get her vests? “That is such a gendered question.” No, it’s not, I say. Jeremy Corbyn famously gets his from a market stall in Islington. “But here's the thing - we do live in an unequal world and when women are asked those questions, it is implicit that if you look a certain way people are more likely to trust you. . . . and those kind of questions is like being asked if we should have two women at the top. All my life it's been men and no one has batted an eyelid. Now there's the possibility of two women, people are saying 'whoa, steady'.”

I am chastened, having thought the vest question was mildly diverting, but that is not the end of my transgressions. A few weeks ago, I wrote a piece which – inter alia – praised Liz Kendall for saying unpopular things at hustings, saying this showed “ladyballs”. The Independent on Sunday’s Jane Merrick picked this up in an interview that weekend with Kendall, who liked the phrase.

But Creasy was not impressed. She first put out a campaign poster which said, “When people ask of women, ‘have you got the balls?’ I say, ‘We can do better – we’ve got the guts’.” Now, she shows me a Grazia piece she has written about sexism, which observes, “Some think women aren’t ‘up to’ the role or that we need ‘balance’ in our leadership team . . . Indeed, some ask if we have ‘ladyballs’ – as though women in senior positions are OK as long as they mimic men.”

Having a public dig at two female journalists while running on a feminist platform is not, shall we say, orthodox political behaviour. But once my miffedness has subsided, I’m oddly impressed. Stella Creasy is not interested in smoothing off her edges in order to get on, or becoming “clubbable” by flattering political journalists. This is me, take it or leave it, is the message.

There is a streak of iron running through her, demonstrated by this unwillingness to let what she perceives as sexism slide. Early in her parliamentary career, she told a story of being mistaken in a lift for a secretary, which ruffled many feathers among established MPs. A few years later, she became the public face of Twitter abuse, after speaking out about rape threats she received on the platform. (Other female MPs receive similar tweets – indeed, a man was jailed for sending Luciana Berger anti-semitic abuse – but most are reluctant to talk about it for fear of seeming weak or whingeing.)

But Creasy is nothing if not fearless, which is what has given her a reputation as an individualist - “a cat who walks alone,” in Gaby Hinsliff’s memorable description. But her supporters reject the idea of a loner, saying the characterisation is driven by her refusal to rely on networks of patronage in the party. “Stella's gone about politics in a different way - not being in shadow cabinet but making her name with more freedom running her own campaigns on the back benches and in junior positions,” says a member of her campaign. “I think the loner thing is nonsense and comes from the fact she just isn't tribal and that unsettles MPs stuck in an old way of doing politics that reduces people to which gang you are in. Some tribal elements of the party feel threatened if you are not in a tribe and so she becomes like a disruptive technology to them - popular with people, found unsettling by established elites and then ultimately embraced by them too.”

Creasy says that her reputation comes from the fact “I do things differently”. She describes the payday lending campaign, which took on companies like Wonga which charged borrowers eye-watering interest rates, as an example of her ability to bring disparate groups together for a common cause – credit unions, trade unions, local councilors and activists. “It was building teams of people who were working in a different way,” she says. “But this is not how Westminster operates.”

To bring more of that spirit into the party, she has an idea: instead of a national manifesto, the party should have a list of priorities. “If you have a campaign idea that is an answer – and when I say it's an answer, it's not "someone should do something about this" but "here's something that would help make a difference" – then you should be able to get matched funding from Labour to be able to campaign for that to make it happen.” This is part of her vision for a less factional party. “We can't afford to waste anyone in the Labour party,” she says. “Most of my adult life in the Labour party it has been Brownite, Blairite, Trot. . . It's a machine on all sides, that says ‘unless you can conform to our gang, we're not interested in working with you’. That has got to stop.”

Some of this feels like a veiled criticism of Tom Watson, who was accused of masterminding a Brownite coup to topple Tony Blair. He has spoken in the hustings of working in the “engine room” of Labour, while the leader is on the bridge. But Creasy’s vision for the deputy leader’s role is different: “You can't do that in back offices in Westminster, you have to want to be out in the field on the front line with people, because it starts with people.” For several years, she has run leadership training sessions for women who want to get into politics, and seminars called “Circular Firing Squads”. Her own feminist connections are impressive: she is friends with Times columnist Caitlin Moran, who is backing her for the deputy leadership, and stand-up Bridget Christie.

But back to how things work – because Creasy has public services in her sights. She tells the story of a woman in her constituency who had 18-month-old twins, who desperately wanted to spend her personal independence payments, part of disability benefit, on a morning’s childcare on a Thursday. “For her, in spite of all her conditions, a morning without the children was gold.” A friend who used the same Sure Start centre wanted the same thing, and together they could have afforded a whole day. “The answer was 'no, that money is supposed to be spent on you and not your children' . . . People power is about giving those women the help and support to be able to make the choice that's right for them.”

But isn’t that a problem people associate with the left? That the state knows better than you do how to spend your money? “What did the last Labour government get wrong? It did lots of great stuff on choice, but nothing on voice. You need choice and voice to work together.” She is passionate about “mutualising services” – OK, but then how do you do that without using the phrase “mutualising services”, I say, which makes me want to cry? “People power.”

There is no doubt that Stella Creasy’s politics differ significantly from Jeremy Corbyn’s – you might once have called her a Blairite, although that term now seems to encompass anyone to the right of Che Guevara – but they are in essence both offering the same vision. It’s the idea that even without power, Labour might make a difference. In Jeremy Corbyn’s case, that is by moving the national conversation to the left. In Stella Creasy’s, it is about working on progressive campaigns with anyone who will muck in. That represents a stark difference with the way the party is used to functioning. She might rage against the machine – but can she break it?