MPs or their staff members have called an immigration enforcement hotline 68 times last year to report on their constituents, it has been revealed.
This has prompted charities to write to Commons speaker John Bercow asking MPs to pledge not to inform on constituents. They argue that people should not have to fear being reported on by their MPs.
The pledge has been signed by 107 MPs, and Heidi Allen is the only Tory, reported BBC. Other Tory MPs argue they "would be expected by most constituents to report any suspected illegal activity".
Of the 68 calls by MPs to the hotline, 34 were from Conservatives, 32 from Labour, one DUP and one Lib Dem.
The immigration hotline statistics were revealed in written questions by Labour MP David Lammy.
The group of charities that wrote the letter - shown to the BBC's Victoria Derbyshire programme - to Bercow, said they would ask people not to seek advice from MPs who did not sign.
"MPs have a responsibility to advocate for all their constituents, regardless of immigration status," the letter reads. "Many migrants are now fearful of contacting their MP, effectively excluding them from democratic representation."
Lib Dem MP Tim Farron, who is supporting the campaign, told the Victoria Derbyshire programme: "It astonishes me that any MP would think that the best way to respond to a vulnerable constituent is to shop them to the Home Office. Many of those immigrants who may be here illegally will be victims of administrative error, dodgy solicitors or even human trafficking."
Akram Salhab, who co-ordinated the campaign for the groups Migrants Organise and Global Justice Now, said that many MPs refusing to sign were confused about their duties. Some have said they will not report people for immigration enforcement, but would do so if they have committed a crime.
"But these are separate issues - if someone has committed a serious crime, they should be reported to the police, not the Home Office," he said.
Plaid Cymru MP Hywel Williams, who recently raised the case of Bangor engineering student Shiromini Satkunarajah, one of his constituents, in the House of Commons - helping to stop her imminent deportation to Sri Lanka, said: "I don't think that MPs should be reporting cases to the authorities.
"This would break the trust between MPs and their constituents. It would also discourage other vulnerable people from seeking help."
Conservative MPs Alberto Costa and Craig Whittaker, who did not sign the pledge, said in a statement that while "sometimes devastating" mistakes had been made by the Home Office, lessons were being learned.
"Like any member of the public, an MP may decide to contact the Home Office to report suspected immigration offences just as he or she would be expected by most constituents to report any suspected illegal activity, not least because that is an obligation we all have."