Lord Macdonald of River Glaven, who served as director of public prosecutions from 2003 to 2008, has called for explicit limits on the crimes covered by the Covert Human Intelligence Sources (CHIS) Bill, according to The Times.

The bill has been introduced to provide a “clear and consistent statutory basis for a limited number of public authorities to continue to authorise participation in criminality, in carefully managed circumstances”.

However, critics have said the legislation could allow state agents to commit serious crimes like murder in breach of the UK’s international human rights obligations.

Lord Macdonald said the bill should explicitly ban “heinous acts” including murder, torture and sexual violence, as was done in a similar Canadian law, rather than simply referring to a human rights framework.

He also called for tougher oversight, requiring independent warrants for crimes instead of only internal authorisation, under which it would be “easier for a policeman to commit a serious crime than to search a shed”.

The introduction of the CHIS Bill follows years of litigation by Reprieve, Privacy International, the Pat Finucane Centre and the Committee on the Administration of Justice, who argued that an existing MI5 policy allowing agents to commit crimes was unlawful.

Last December, the Investigatory Powers Tribunal (IPT) ruled by a 3-2 majority that the policy was lawful, but the NGOs said they would appeal the “knife-edge” judgment to the Court of Appeal.