Aisha laughs out loud at the thought of how her colleagues and clients would react if they knew she shares a husband. The laughter makes her loose hijab slip slightly, exposing a few strands of dark hair. “They would be dumbfounded and probably prurient,” she sniffs. As far as they are concerned, her 42-year-old factory-owning husband has only one wife—this thoughtful attorney sipping Earl Gray tea in the sitting room of a pleasant and very middle-class Edwardian house in a leafy residential road in northwest London.

Her immediate family and close Muslim friends know the truth: 41-year-old Aisha is a second wife and for three years has been conveniently—at least for her—sharing her businessman husband with his first bride. “It was my choice to marry him. There was no coercion.” With a wry giggle she says: “I wanted a partner and man-hunted for one using a marriage agency and this suits me.”

“I didn’t want to remain single and I wanted my relationship to be endorsed by my religion, so sleeping around or living with a non-Muslim wasn’t an option,” she says. “This works for me.”

Being a co-wife is a situation that apparently works for other successful British Muslim women, who have delayed marriage to build careers and discover that by the time they are ready for a husband, their age counts against them and they don’t have the pick of the crop. For them, sharing a husband is a practical solution that allows them a suitable partner and stable companionship all sanctioned by Islam.

And it has the added bonus of allowing the women to retain the independent lives they have developed for themselves during their single years. “I didn’t want a full-time husband,” Aisha says firmly.

She admits that the first wife, whom her husband married 15 years ago in an arranged union, wasn’t initially happy with the arrangement but has “come round,” although the two wives have little to do with each other and seldom meet. Aisha sees her husband on alternate days and nights—although if either of the two children from his first wife falls sick, or there’s a family emergency, Aisha will be compensated for any time lost as a result of timetable changes.

The unexpected trend of professional British Muslim women agreeing to become second or third wives has startled Islamic religious leaders, some of whom disapprove, and is now gaining political attention with British Conservative politicians vowing to stamp out the practice—although how theoretically they will accomplish this remains unclear. Under U.K. law multiple marriage is illegal, but co-wives are exploiting loopholes.

The attitude of these co-wife professionals stands in marked contrast to those of many liberal female activists in the Middle East, where, in the wake of the Arab Spring, polygamy is experiencing an upsurge.

Under dictators such as Egypt’s Hosni Mubarak and Libya’s Col. Muammar Gaddafi, multiple wives were discouraged. Now, the issue has become a clashing point in the region’s culture wars. In February, liberal activists in Libya bristled at an Islamist-inspired judicial decision that makes it much easier for men to take on multiple wives. Activists such as Farida Allaghi, a veteran human-rights campaigner and founder of the Libyan Forum for Civil Society, warned Islam was being hijacked by men and argued the Arab Spring was seeing a lurch toward religious conservatism.

But the part-time wife trend in Britain would seem to be less of an expression of religious conservatism and more a reflection of what could be described as Muslim libertarianism. The professional Muslim women say they are adapting Islam for their purposes and making it work for them in the modern Western world. They are the proactive ones, seeking to be co-wives, rather than being pressed into such marriages, say Muslim dating agents.

Bigamy (having two wives) and polygamy (having more than two) were first made illegal in England and Wales in 1604 and in the 17th century carried the ultimate punishment—the death penalty. Now a conviction for either can be punished with up to seven years in prison. Technically, though, Aisha’s marriage doesn’t exist. Like other polygamous Muslim marriages in Britain, it was enjoined under Islamic Sharia in a religious ceremony known as the nikah that isn’t recognized automatically by British authorities—and thus doesn’t fall afoul of British law. Muslims can register their Sharia-sanctioned marriages officially with the state but most don’t unless there’s a pressing immigration reason to do so. And those who enter polygamous marriages are certainly not going to open themselves up to being prosecuted.

With the marriages being conducted in nikah ceremonies before one of Britain’s more than 80 Sharia councils, or in the privacy of private homes, no one has reliable statistics on the polygamy trend. And fearful of prompting a non-Muslim backlash, polygamous families tend to be wary of talking with the media. Three years ago, the British government estimated that perhaps a thousand Muslim men were bigamists or in polygamous relationships, but some Muslim community leaders believe that figure is way off and their estimates range as high as 30,000 men. Some suspect it could be even more commonplace and one London doctor confides that several of his Muslim patients in the district of Vauxhall, just south of the river Thames, are involved in bigamous or polygamous marriages. “I saw two co-wives simultaneously the other day,” he says.

Across the country, Sharia councils and Muslim marriage agencies are reporting a dramatic increase in the number of women willing to be co-wives, especially women in their 30s and 40s. In stark contrast to the past, when bigamy and polygamy were more often than not something associated with poorer and more working-class first-generation immigrants, now many of the women are like Aisha—university educated, successful when it comes to their careers, and firmly middle-class.

This is far removed from the picture of demeaning exploitation that non-Muslim British critics of polygamy present in arguments for the banning of the Sharia-sanctioned practice.

Britain’s Sharia councils have been unpopular among Conservative Party lawmakers since the mid-1990s when they were accorded limited semi-official status and allowed under British civil law to arbitrate some legal disputes involving family law or financial contracts. There are now more than 85 Sharia councils—from London and Manchester to Bradford and Nuneaton—and they operate mainly from mosques. Critics fear the courts are eager to expand their reach and they argue their values are inimical to Britain’s liberal traditions. Recently, the councils were in the news after an undercover BBC television documentary team found Sharia judges unsympathetic to wives suffering physical domestic abuse. Sharia judges were pressing abused wives to return to their husbands and avoid the police.

For Conservative peer Baroness Cox, Sharia councils detract from the idea that everyone in Britain should fall under a single legal code and she says they effectively create a parallel quasi-legal and moral system that treats people differently depending on their religion. She points to the growth in polygamy as evidence of this. She has been pushing a measure to curb Sharia councils. However, short of outlawing the councils from presiding over any marriages—a move that would provoke a Muslim outcry and deprive Muslims of a religious ceremony—it isn’t clear how her measure would stop polygamy.

Cox argues that there are two polygamy trends underway in Britain: that of the part-time wives, like Aisha—and another “where the majority of co-wives are the ones living a more Taliban-like existence in very closed communities who can’t get out, can’t speak, and are trapped and a lot of them are suffering.” She says that the professional, articulate women are out and about and more visible but worries they are “not typical of the majority of co-wives trapped in the more closed communities, who have been brought over from countries like Pakistan, Yemen, and Afghanistan and are often illiterate and terribly unhappy.”

She worries that second wives have no real legal protections if the relationships fall apart—nor do the children conceived in any such marriages. “Our duty to safeguard the vulnerable seems in danger of being undermined out of sensitivity towards some minorities,” she says. Other politicians maintain that by failing to confront polygamy in either guise, Islamic conservatives are being empowered indirectly and modernizing Muslims are being thwarted.

But Mizan Raja of Islamic Circles, a community-based nonprofit in London that runs Muslim marriage events, says this is a simplistic way of looking at polygamy and that there’s no neat split between modernizers and religious conservatives. The women he deals with who are becoming co-wives would consider themselves modernizers—in fact trailblazers, shaping Islam to conform to their very modern lifestyles, he insists.

“I am seeing divorced or widowed women and women in their spinster years, wanting to become co-wives. It is the women coming forward wanting this, not so much the men,” Raja says. “They say, ‘I have a career, I have a business, but I don’t have time for a full-time husband. I want a stable relationship, but it needs to revolve around my schedule.’ This is a creative way to be in a stable relationship. For them a key thing is not to be stuck in a full-time marriage: they want some strings attached and don’t want other strings.”

Of course, some conservative Muslims frown on the “some strings attached” attitude to marriage, arguing that it is too flippant and misunderstands the obligations and responsibilities that are at the heart of Muslim marriage. While the Koran permits polygamy—it did so as a protection for women who remained unmarried, especially widows whose men had fallen in battle—marriage entails some specific obligations on men, including treating all wives fairly and equally, not just materially but emotionally and sexually as well.

Sheikh Ibrahim Mogra, an influential member of the Muslim Council of Great Britain, recently warned that being able to complete this duty was beyond most men. Even keeping a secret second wife is a breach of the Koran, since it fails to treat both wives equally. And marriage just for sexual gratification is not a valid reason to wed. The Muslim conservatives say part-time wives are little more than mistresses.

The spurt in polygamous marriages was first noticed about four years ago when Britain’s Sharia councils saw an unprecedented jump in inquiries about polygamous marriage. It shows no signs of falling off, observes Khola Hasan, a Muslim scholar who advises the Islamic Sharia council in the inner London suburb of Leyton. “There’s a definite increase in polygamous marriage,” she says. “Sharia councils are seeing it and marriage agents are encountering it. When I was younger, 20 years ago, this was almost never heard of and we never talked about polygamy at home, but now it is becoming much more common and I don’t see any signs that this is just a fad.”

She agrees that professional women—generally third- or fourth-generation immigrants—are drivers behind the part-time wife trend and that they have a clear idea of what they want. “Traditionally women married in their early 20s but now they are delaying marriage to study and to establish careers and before they know it they are in their late 30s and partners are hard to find,” Hasan says. “Also, we are seeing more divorce among Muslims—from being rare it has jumped to one in eight of Muslim marriages ending in divorce, and for divorced women it is easier to find a husband who wants a second wife.”

She adds: “If they have children from a previous marriage, they often prefer to be part-time wives—they may not always want the husband around. They are happy to have the support when they need it from a partner but like to focus on their children.”

That’s a reason cited by Nazia, a 34-year-old social worker, for her part-time marraige. She lives in an outer London suburb south of the capital with her two small children, whose father died in a car accident. For several years she remained single before meeting and marrying her accountant husband. He was married already to a distant cousin from Pakistan. “It was an arranged marriage and they have little in common—he’s well-educated and she’s not. With me he can be more himself. But he would never divorce her and his parents accept me, although it took them time. I get on with his sisters very well, and I do see his first wife every now and again. We are not best friends or anything, but it is OK.”

She says she thought long and hard about the marriage. She wanted her children to have a male figure around but didn’t want to have to share her kids the whole time. “This way I get my space and time with the children, and when I need a man, there he is.” She is uncomfortable talking about what the arrangement must be like for the first wife, and how she might have felt when the news had been broken to her by her husband that he was taking a second wife. “Well, not great, I suppose,” Nazia offers. According to Sharia councils, polygamy is now among the top 10 reasons cited by women wanting to divorce.