On Tuesday, Theresa May issued an official call to the UN to take action against modern day slavery, complete with a puff piece in the obliging Evening Standard. The Prime Minster was hamming up the empathy, gushing about the plight of modern day slaves – those working in illegally bad conditions for poverty wages, perhaps exploited by an unscrupulous people trafficker.

"How can anybody treat another human being like that?" she said to the Standard. "How can anybody think that they can put another human being through all of that pain and suffering, and use them just as an object?"

Modern day slavery has been a passion project for Theresa May for some time. As Home Secretary in 2015 she introduced the Modern Slavery Act, which is hyped as a trailblazing piece of legislation. She made a very similar call to the UN this time last year. But she's got another hobby-horse galloping away in the opposite direction. Since 2012 she's been obsessed with making Britain a "hostile environment" for migrants. Only thing is, a hostile environment for migrants is a perfect environment for exploitative employers.

Today, VICE can reveal how her government's migration policy is contributing to the problem by dangerously conflating the goals of ending exploitative labour and cracking down on immigration. Documents VICE obtained by Freedom of Information request reveal the existence of an agreement between the Department for Work and Pensions, HMRC and the Home Office, which details how the departments cooperate and share data to get undocumented migrants out of the country. The documents shed further light on how, away from the public eye, the government is creating borders throughout everyday life, driving undocumented people further underground, away from legitimate channels.

Gracie Bradley, Advocacy Officer at Liberty, said, "Theresa May's obsession with creating a 'hostile environment' for migrants at any human cost – and the policies that have come with it – are an exploitative employer's dream."

The agreements talk about "the opportunity to stop illegal work in the UK" and aim for "the removal of incentive to remain in the UK potentially leading to an increase in voluntary departures for those that are in the UK". This is the euphemistic logic of the hostile environment: get people to "voluntarily" leave the country by "removing incentives", AKA ensuring they have nowhere left to turn.

So the idea they're selling is: crack down on illegal slave jobs. Slaves, relinquished of their horrible jobs, go home. No more migrant slaves in the UK.

But that's not what's going to happen.

The reality is almost the complete reverse. "Far from cracking down on illegal working, these agreements create it," said Bradley. "They will push undocumented people out of taxpaying jobs and into the shadow economy, where they will likely work cash in hand and experience the very abuse and exploitation the Prime Minister has so vocally condemned this week."

The fact is, taking away people's options does not make them leave the country. Caroline Robinson, policy director at Focus on Labour Exploitation, said: "There is no evidence that 'hostile environment' measures work to persuade people to voluntarily leave the UK, however there is a growing body of evidence of the way in which such measures drive people into increasingly precarious work and labour exploitation."

If this Sophie's Choice doesn't make a migrant leave the country – "voluntarily", of course – there's always the option of "enforcement action", which means deportation, possibly preceded by a lengthy stay in a migrant detention centre.

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The documents detail how HMRC and the DWP will help the Home Office find "up to date contact information on immigration offenders with whom we've lost contact, enabling us to take enforcement action with those not compliant". It also explains that data will be shared even on cases whose status ended prior to 2008. That means they'll be snooping on people who have been in the country for at least eight years – long enough to establish lives and, probably, legal grounds to remain. It's worth bearing in mind that Home Office databases are sprawling and sometimes wrong, which is how we end up with stories about people who were born and raised in Britain, with British families, going through the stress of being told to leave the country.

The documents reveal how the Home Office will issue "nudge letters" to employers who have staff whose leave to remain has expired. Bosses have already been complicit in screwing over migrant workers, like when burger chain Byron infamously cooperated with immigration raids. A tap on the shoulder of their bosses from the Home Office will do nothing to help those workers. The threat of shopping you to the border agencies is a boon to any unscrupulous employer wanting to keep workers scared and compliant. "Offering employers the chance to collaborate to remove undocumented workers and criminalising the worker creates a total power imbalance and offers the chance for unscrupulous employers to abuse and exploit workers with impunity," said Robinson.

Even with a scarily intrusive state apparatus, Theresa May wants us to be on the look-out for modern day slaves. "If somebody uses a nail bar, for example, they should ask themselves about the people working there. Do they always cover their faces? Do they appear to be nervous?" she said. "The key thing is for victims to feel they have the confidence to come forward and be given the support they need."

So, what confidence-building support is out there? The National Referral Mechanism for victims of human trafficking or modern day slavery is part-run by... the Home Office. So the confidence-building support for exploited workers is run by those fixated on chucking them out of the country at the first opportunity. I asked the Home Office what support would be offered to undocumented people and whether their migration status would come into play, and they didn't get back to me.

Activists have pointed out that the discussion around modern day slavery is unhelpful. Sensationalising the worst examples is a neat way not to talk about the continuum of exploitation, which exists throughout the labour market, and which is best solved by workers organising themselves. But the government's conflation of migration and labour exploitation is evident even in the personnel involved. In January, Sir David Metcalf was named as the first Director of Labour Market Enforcement, tasked with cracking down on exploitation in the workplace. Previously he had been director of the Migration Advisory Committee.

It's not that surprising that labour issues are being viewed through the lens of migration. The Home Office is fixated on it, and on extending their reach throughout the state. One of the documents released to VICE notes that "the Home Office is committed to developing closer links with other bodies with common interests in tackling non-compliance with legislation". Already, similar agreements with other departments have seen NHS patient data and the personal details of school children handed over to the Home Office. Doctors and teachers are being turned into border guards. The Home Office has a tip-off hotline so you can grass up any migrants you encounter. The police have even handed over victims of crime to the Home Office. "Right to rent" checks means your landlord is checking up on you.

"These are the latest in a string of unfettered Home Office data-sharing agreements set up in total secret and only exposed by press or campaigners," said Bradley. "So far we know there are others with the Department for Education, NHS Digital and the Greater London Authority. Clearly this government feels it can trawl through people's sensitive personal data at will without the inconvenience of public knowledge or consent. Right now, the target is undocumented migrants – but the precedent that sets for all of us is clear and disturbing."

To say May's concern for so-called modern-day slaves contradicts her migration policy would be one way to look at it, but really there's no contradiction. When the "support" the government give to vulnerable people is to make them go away, what we're seeing is the caring face of a government that will stop at nothing to kick people out.

Update – Following the publication of this story, a government spokesperson got in touch with the following statement:

"We have long-standing arrangements to share information between DWP and the Home Office to improve efficiency, protect taxpayer's money, and tackle illegal working and immigration offending. Access to this information is strictly controlled with strong legal safeguards.

"We operate a fair immigration system in accordance with legislation agreed by Parliament and we expect those with no right to remain in the UK to leave voluntarily.