Writing in the News Letter, Belfast solicitor Neil Faris and Peter Smith CBE QC, who served on the Patten Commission, said the structures agreed under the Stormont House Agreement in 2014 would undermine “cardinal democratic freedoms”.

The structures formed the basis of a draft bill published in 2018, but their implementation has been thrown in doubt by more recent UK government proposals which break with the 2014 agreement.

In their article, Mr Faris and Mr Smith highlighted the proposed ability of the HIU to produce comprehensive reports for the families of victims of the Troubles, which could include the names of individuals believed to be responsible for particular killings.

The lawyers wrote: “Such a proposal, improperly in our view, would combine in the new body not only police powers but also the power to make adjudications or findings against individuals in its reports which it would issue to victims’ families.”

They continued: “To put it simply, the police have the right and duty of investigation and fact finding in respect of crime – for the purpose of making reports to the PPS.

“But the 2018 draft bill in our view abused these by conferring also on the HIU the power to make adjudications against individuals, whether or not there is any allegation of any criminality.

“It is only in a ‘police state’ that the police have such a role – designed to exclude the courts!”