You see them sometimes in the kitchens and nurseries of wealthy people – women, mostly Filipino, rarely introduced by name. They come to the UK with a promise of income and regular hours, working as housekeepers or nannies to send money back home to their own families; but for many of them the reality is shockingly different.

There are nearly 19,000 people on overseas domestic visas in the UK, according to a Freedom of Information request from the Home Office seen by the Guardian; and together they make up, like the Windrush generation, a population of migrants under threat.

As part of Theresa May’s “hostile environment” policies as home secretary, the UK government changed the law in 2012 so that migrant domestic workers (MDWs) could only come to the UK on a non-renewable six-month “tied visa” – one that bound them to a single, named employer. This means that if their employer is exploitative or abusive, their main means of escape – moving to another employer – is closed to them.

Mel, a 36-year-old domestic worker from the Philippines, describes being brought to London in 2009 by a Saudi family. Her contract guaranteed her a £1,500-a-month salary; in fact, she was paid nothing. She worked most days from 6am until at least 1am and slept in the laundry room. After four years, she managed to escape with the help of a Filipino friend who was a member of the Voice of Domestic Workers (VODW), a grassroots self-help group. Since then she has been undocumented, working as a volunteer for VODW, which supports her.

“Why should escaping from an abusive employer be a crime?” she asks, but five years after she fled her host family, the law caught up with her. At 7.45am on a cold morning in December, Mel heard a loud knock on her front door. She opened it to find four immigration officers. They arrested her and spirited her away in a white van to Becket House, an immigration reporting centre near Tower Bridge in London, where she was photographed, fingerprinted and invited to return voluntarily to the Philippines. Just going back home is not an option for Mel and the women like her: her earnings would be so meagre that there is no way that she could support her children.

The contract that Grace, 45, also from the Philippines, signed with the Kuwaiti family who brought her to the UK was for £1,200 a month, she recalls. She was paid just £220. Like her fellow domestic workers, she sent most of her earnings back home. Grace went abroad to lift her four children out of poverty – “to give food to your kids, pay for school uniform, books, transport – and hospital”. She worked seven days a week – no days off or holidays. What if she got sick? “You needed to get up!” she says. Grace wasn’t allowed out unaccompanied; when, two months after she arrived, her employers went to France on holiday, they locked her in the house alone for a week. A cleaner from a neighbouring house, hearing her sobbing, put a ladder up against the back balcony, enabling her to escape with her possessions in a black sack. Grace is now undocumented and dependent on “good Filipinos giving me odd jobs” to get by.

Lucy, 46, weeps as she talks of her three children, aged 27, 18 and 13, whom she hasn’t seen for seven years, as a consequence – she says – of her employer pretending to renew her visa, but never doing so. Her husband back in the Philippines, who had diabetes, urged her to come home but, as she was taking her case to the high court, “I said let’s wait – and then he died. We’d been married for 23 years.” Lucy’s appeal failed. “I went crazy, I was thinking of suicide. Now I’m OK, but it’s so sad.” Lucy is now working “underground”, for an employer who is aware of her situation but pays her a living wage.

Before 2012, an MDW could renew their visa over a period of five years and then apply for indefinite leave to remain and ultimately British citizenship. This was the route taken by Marissa Begonia, a VODW founding member and coordinator.

After lobbying by VODW, the trade union Unite and Kalayaan, a charity for domestic workers, the government commissioned an independent review of the UK’s domestic visa policies in 2015. Attaching the visa to a specific employer, the review found, increased these women’s vulnerability to exploitation, while living outside the law “increases their vulnerability to further abuse”. The report’s author, James Ewins, recommended an unconditional right for migrant domestic workers to change their employer and the right to apply for an annual extension of their visa for a maximum of two-and-a-half years.

The government rejected this recommendation. All it did, in 2016, as part of the Modern Slavery Act, was slightly modify the harsh restrictions it had introduced in 2012. A MDW now could change employer, but only within the six-month original visa period, which could not then be extended. In reality, most workers have to leave – or go underground.

Facebook Twitter Pinterest Marissa Begonia. Photograph: Lauren Maccabee/My Home Is Not My Home

In 2011, the UN International Labour Organization introduced the Domestic Workers Convention to improve the living and working rights of domestic workers. It has been ratified by 26 countries – including Ireland, Germany and Italy – but the UK is not among them. Meanwhile, migrant domestic workers in the UK remain mostly unprotected by laws that the rest of us take for granted – they are not covered by health and safety laws, for example, or the Working Time Regulations 1998, and employers often don’t comply with the national minimum wage – as Mel and Grace know only too well.

When VODW polled its members, it found that, of the 500 who responded, 76% had experienced verbal or physical abuse, and that they worked on average 91 hours a week. Some had even had their passports confiscated by their employers. Because of the hidden, private nature of the work and because many are unable to speak English, these women are socially isolated. There are few examples of true modern slavery, but these are undoubtedly some of them.

“Their status as workers is blurred by the language – like ‘maids’ or ‘domestic servants’ – that’s used to describe them,” says Joyce Jiang, a lecturer at the University of York and researcher into the experiences of immigrant workers. Many of these women have had to leave their own children to look after those of their employers – and because of the intimate nature of the work, they are often seen as “labourers of love” or “part of the family”, which obscures how little they are paid.

I asked the Home Office whether it planned to change the rules regarding MDWs, to allow these women, many of whom have lived and worked here for years, the right to stay legally. It pointed me to the National Referral Mechanism (NRM), a framework for identifying and supporting victims of human trafficking that, since 2016, also encompasses slavery, servitude and forced or compulsory labour. The MDWs who go down this route successfully can get a two-year visa, after which they must return home. But it’s an imperfect solution, says Begonia. “You need to have been raped, beaten or starved to death to get it. If you’re not paid for months, is that not abuse or servitude?”

Those in abusive workplaces who don’t apply fall back on the services of VODW. Begonia, Grace and the others constitute a remarkable rescue service. They distribute cards written in Tagalog, Hindi and Indonesian offering help and a phone number. When called, they go to a MDW’s home, wait outside and then escort them to safety. “Sometimes they don’t even know the address, so we tell them to look for an envelope that has it. Or if they’re working in a hotel, we tell them to phone reception,” says Begonia. VODW has rescued 80 women in this way.

Now, in collaboration with Jiang and the film-maker Tassia Kobylinska of Goldsmiths, University of London, VODW has produced a video and exhibition, My Home Is Not My Home. As part of the project, funded by the University of York, Kobylinska worked with a group of migrant domestic workers, teaching them how to frame images and record audio so that they could document their lives on their phones. The exhibition includes an MDW’s white uniform, a job contract, the clothes that one MDW wore when escaping and letters from their children. “To put these things in a gallery makes them valuable. We hope that this will bring into the public domain what has festered behind closed doors. It can be used in evidence as part of their campaign [to remain here],” says Kobylinska.

Begonia herself trod this path. “It was the most difficult and painful decision of my life to leave my children behind when they were one, two and three. I wanted so much to be a normal mother who could look after them physically – but my sister was their mother, really, and not me … what kept me going was the dream that we could one day be together again.” For her, the story has a happy ending. She has become a formidable voice for MDWs – lobbying parliament, speaking at the UN on behalf of VODW, for which she works part-time (she is still a domestic worker the rest of the time). Her three children now live with her and work in the UK.

Of the others, Mel has been referred to the NRM. Lucy and Grace, however, remain undocumented. For them, in every sense, the UK is far from home.

Some names have been changed. My Home Is Not My Home runs from 16 to 26 January at L’Etrangère, 44a Charlotte Road, London EC2