Two DUP MPs voted in favour of a Government bill which does not formally ban undercover agents and informants from committing murder, torture and rape.
Jim Shannon and Gavin Robinson were among 313 MPs to vote in favour of the controversial Covert Human Intelligence Sources (Criminal Conduct) Bill, which allows public authorities, ranging from police and MI5, to authorise agents and informants to commit crimes while undercover.
The House of Commons, however, rejected an amendment to limit the type of crimes, such as murder, torture and rape, that can be authorised under the Bill.
Alliance's Stephen Farry and SDLP MPs Colum Eastwood and Claire Hanna were among 98 who voted against the Bill, which was passed on its third reading and will now go on to be scrutinised by the House of Lords.
The Bill would enable the police and MI5, as well as HMRC and the Food Standards Agency, to authorise actions not only issued in the interests of national security or preventing and detecting crime, but also preventing "disorder" and in the "interests of the economic well-being of the UK".
If the Bill is approved by the Lords it would also apply to Northern Ireland, a move which would prove controversial given alleged state collusion in a number of high-profile cases. These include the 1989 murder of Belfast solicitor Pat Finucane by loyalists alleged to have acted in collusion with the security forces. His family have calling for a full public inquiry into the killing.
The DUP said the covert human intelligence sources play a "crucial part" in safeguarding the public from very serious crimes, including terrorism.
"No criminal conduct can be authorised unless it is proportionate and necessary for the preservation of national security, to prevent economic harm or potential loss of life," it explained.
"That is over and above the confirmation by the (Security) Minister that it would never be permissible for a covert source to engage in sexual relations or for it ever to be used as a tactic of deployment. There is an absolute and unfettered ban on torture and the amendment was therefore unnecessary, but it was acknowledged during the debate that it was right these issues were raised and considered."