The confidential patient records of more than 8,000 people have been handed over by the NHS to the Home Office in the past year as part of its drive to track down immigration offenders.

A memorandum of understanding, published for the first time on Tuesday, makes clear that NHS digital is required by law to hand over non-clinical patient details including last known addresses, dates of birth, GP’s details and date registered with doctor.

The latest figures show that the number of Home Office requests have risen threefold since 2014 as the government has stepped up Theresa May’s drive to “create a hostile environment” for illegal immigrants in Britain.

Patients and migrants’ rights groups have expressed serious concerns in the past over the use of NHS records to track down immigration offenders and warned there is a real danger it could deter some from seeking medical help for themselves or their children.

Department of Health figures show that the Home Office made 8,127 requests for patient details in the first eleven months of 2016, which led to 5,854 people being traced by immigration enforcement. The first three months of 2014 saw just 725 Home Office requests compared with 2,244 between September and October last year.

The disclosure of the scale of the use of NHS records for immigration enforcement follows a similar agreement between the Home Office and the Department for Education to share the details of up to 1,500 pupils a month to trace potential immigration offenders.

The legal powers requiring the NHS to share confidential patient information records are contained in obscure exemptions in the Health and Social Care Act. The new memorandum of understanding (MoU) with the Department of Health published on Tuesday justifies their use, saying it is in the public interest that UK public services, including the NHS, jobs, schools and housing, should be protected from unnecessary pressures.

“The information to be disclosed under this MoU is administrative in nature and consequently falls at the less intrusive end of the privacy spectrum, making disclosure easier to justify as the public interest threshold is lower,” states the MoU.

A government spokesperson said: “We share limited information between health agencies and the Home Office to trace immigration offenders and vulnerable people, and prevent those without the right to access benefits and services doing so at the expense of the UK taxpayer.

“Access to this information is strictly controlled, with strong legal safeguards. No clinical information is shared, and before anything at all is shared there has to be a legal basis to do so. Immigration officials only contact the NHS when other reasonable attempts to locate people have been unsuccessful.”

The requests involve potential offenders whom the immigration authorities have lost contact with and have failed to comply with reporting restrictions, absconded or escaped from immigration detention or have overstayed their visa time limit.

The MoU makes clear that NHS Digital retains the right to seek more information from the Home Office should they need to and “without limitation, NHS Digital may refuse a request for information from the Home Office if it is not satisfied that the request is in the public interest”. However the latest figures show that only 69 requests out of 2,244 were refused between September and November last year.

The Home Office said that no-one is denied urgent treatment and vulnerable people, including those seeking asylum and refugees, are not charged for NHS care they receive. But it said it is increasing the numbers of people leaving Britain voluntarily by sharing information across government to deny access to benefits and services to those who are here illegally, and making it more difficult to access private rental and financial services.

Diane Abbott, shadow home secretary, said: “This is unacceptable. We have already seen this government using schools to gather immigration data on children. Now we find they are using the NHS in the same way.

“Other public services should not be expected to cover for this Tory government’s cuts to the border agency. People could be deterred from seeking medical care because they are worried their confidential information might be passed on. This could do irreparable damage to the people concerned and it may have public health implications. It should stop now.”