A former chief constable investigating "heinous" murders in Northern Ireland linked to collusion with state security forces has condemned the Government’s attempts to ban any future prosecutions.

Jon Boutcher, the head of Operation Kenova, said the proposals did not "sit comfortably" with him and expressed his alarm that the ministers were planning to abandon the “rule of law” in order to protect former soldiers from being taken to court.

Mr Boutcher’s intervention adds to growing pressure on Brandon Lewis, the Northern Ireland Secretary, over his intention to introduce a statute of limitations that would end all prosecutions for incidents up to April 1998. 

The new legislation would apply to ex military veterans but also to terrorists.  

Mr Boutcher, the former chief constable of Bedfordshire, is investigating a series of murders, torture and kidnappings linked to a British agent – known under the codename Stakeknife – and any collusion in those crimes with the British Army and security services.

Mr Boutcher said: "The rule of law has stood us incredibly well. To take away the hope, the prospect, the potential of justice for these families, and these are some of the most heinous crimes committed in the United Kingdom in modern history, certainly doesn’t sit with me comfortably.

"I read the paper last night as many families will have done, and my phone rang off from families who were in tears.

"These families have been let down, given unfulfilled promises and endured countless setbacks, but always conduct themselves with the greatest of dignity and humility."

‘Draw a line’

Mr Boutcher’s comments come as the SDLP is seeking to recall the Northern Ireland Assembly from its summer recess to challenge ministers.

The proposals, which Prime Minister Boris Johnson insisted would allow Northern Ireland to "draw a line under the Troubles", would also end all legacy inquests and civil actions related to the conflict.

SDLP deputy leader Nichola Mallon said: "To shut down justice and close off avenues for truth and reconciliation by providing an amnesty to state agents and paramilitaries involved in the most serious Troubles-related crimes, including murder, is absolutely abhorrent.

"These proposals are hostile to the interests of victims and survivors, they are opposed by all Executive parties and the British Government must withdraw them now.”

DUP leader Sir Jeffrey Donaldson said a process had to be agreed which would allow victims to pursue justice.

"We have made our position clear to the Government, we want to agree a process that enables those victims and families that want to pursue justice to be able to do so, and I think it is wrong to deny them the opportunity of pursuing justice,” said Sir Jeffrey. 

Church leaders have also condemned the Government plans, with the head of the Catholic Church in Ireland Archbishop Eamon Martin saying they will be seen by many victims as a "betrayal of trust".

Breaching obligations

Meanwhile, Simon Coveney, Ireland’s foreign affairs minister, has claimed that the UK’s plans would breach its international obligations and would undoubtedly be tested in the courts.

Having warned on Wednesday that the plans for a statute of limitations were "very much not a done deal", he wrote in The Guardian: “In our view, this would be politically and legally unsustainable, and would damage relationships and trust critical to the protection of the achievements of the peace process.

“We do not believe an approach based on a general statute of limitations would be compatible with the obligations of the European convention on human rights.

"It would undoubtedly be tested in the courts, and if it failed there, it would only add years of uncertainty and misery for families with no benefit.”

It comes after The Telegraph revealed that Brandon Lewis, the Northern Ireland Secretary, has received legal advice warning that acting unilaterally could heighten the risk of a challenge being successfully brought at the European Court of Human Rights in Strasbourg.