The Home Office is obtaining patient data from the NHS and using it for immigration enforcement purposes, despite suggesting last year that this form of data-sharing would no longer take place.

A report by the chief inspector of borders reveals immigration enforcement teams are using hospital records containing data on migrants with an outstanding debt to the NHS of £500 or more.

As well as using the information to encourage patients to repay their debt, immigration compliance and enforcement teams can use it to amend someone's reporting restrictions, encourage their voluntary departure or detain them, the report states.

The government was last May forced into a climbdown over its use of NHS patient information for tracing minor immigration infractions, conceding the bar for breaching patient confidentiality “should be significantly higher”.

After years of pressure from doctors, MPs and charities, ministers pledged to only seek patient data – which was handed to the Home Office by NHS Digital on request through a memorandum of understanding – in the event of serious crimes.

The government said it would now only request information, such as names, addresses and ages, of people being considered for deportation in cases involving “serious criminality”.

But the new report, published last month, revealed that data about any migrant who has a debt of more than £500 with the NHS can be used for immigration and enforcement purposes as a “compliant environment tool”.

Doctors of the World’s policy and advocacy manager Anna Miller said the practice “confirmed patients' worst fears" – that information they give to NHS hospitals could be used to "arrest them in their homes".

She added: “At our clinic we see patients too afraid to get the hospital care they need because of the risk of large bills and concerns about how their information will be used by the Home Office.

“And it places doctors and nurses in an impossible position. Whilst hospital trusts are reporting people to immigration enforcement teams, it is very difficult to build a trusting relationship with patients."

The report found there was little engagement with relevant NHS trusts about the debtor data, and that a "low" number of trusts made use of the Home Office’s Immigration Enforcement Checking and Advisory Service (IECAS).

Chai Patel, legal policy director at the Joint Council for the Welfare of Immigrations, said using the NHS as a “tool of immigration enforcement” meant people who are sick and in need would be afraid to come forward for medical treatment.

“It corrupts the relationship of trust between doctor and patient and fundamentally undermines the commitment of the NHS to treat patients according to need, without asking questions,” he added.

A Home Office spokesperson said: “When overseas migrants incur a debt to the NHS of £500 or more, their future immigration applications may be refused until the debt is settled. In such cases, all the circumstances are carefully considered in reaching the immigration decision, including human rights arguments which may override the existence of the debt.