Northern Ireland’s attorney general has been left isolated after political leaders in London, Belfast and Dublin distanced themselves from his controversial proposal to end prosecutions in Troubles related murders.

Many relatives of those killed during the conflict by republican and loyalist paramilitaries and state forces have expressed outrage at the suggestion by John Larkin QC that those perpetrators yet to be caught should not face justice.

While a concerted demand for Mr Larkin’s resignation has not materialised, Stormont’s leaders are under increasing pressure not to reappoint the lawyer when his term of office ends next year.

As well as a halt on future prosecutions, the chief legal adviser to the power-sharing Executive also advocated ruling out further inquests and inquiries into the crimes committed during the 30-year conflict, insisting a line should be drawn on offences perpetrated before the signing of the 1998 Belfast agreement.

Reacting to the contentious proposals during Prime Minister’s Questions in the Commons, David Cameron made clear the Government had no plans to legislate on any form of amnesty. “The words of the Northern Ireland attorney general are very much his own words,” he told MPs.

Mr Larkin has claimed his proposals do not amount to an amnesty, but has been challenged to explain his rationale, given that perpetrators would not be brought to book.

Troubles crimes are already treated somewhat differently in the eyes of the law in Northern Ireland. Anyone convicted in the present day of a conflict-related offence committed pre-1998 can only be sentenced to a maximum of two years in prison while effective amnesties have been offered to those engaged in decommissioning weapons or co-operating with the search for those “Disappeared” victims whose remains have never been found.

But a blanket block on future Troubles prosecutions, as envisaged by Mr Larkin, would be new territory entirely. Such a radical development could only happen with sufficient support within the Stormont Executive.

That looked like an impossibility after Mr Larkin’s stance was heavily criticised in Belfast by politicians on both sides of the traditional divide, with the Democratic Unionists, Ulster Unionists and the Social Democratic and Labour Party (SDLP) all voicing objection.

Stormont justice minister and Alliance party leader David Ford said he did not agree with the attorney general. “Justice must be a crucial aspect of a victim-centred, comprehensive approach to the past,” he said. “We need a process that includes justice, truth and reconciliation — I don’t believe that we will get any one of these without the other.”

Sinn Féin, meanwhile, has not explicitly endorsed or condemned the attorney general’s stance.

Taoiseach Enda Kenny said it would be difficult for families to accept such a move, especially if incontrovertible DNA evidence linking an individual to a killing was to emerge. “Families want closure, but there’s always that yearning to find out what happened, who gave the instructions, why was this done?” he said.

Former US diplomat Dr Richard Haass is currently trying to achieve political consensus on a number of issues as yet unresolved during the peace process - one of which is how Northern Ireland addresses the legacy of its violent past and the seemingly endless unanswered questions over killings carried out by all sides.

Mr Larkin, who has outlined his proposals in a submission to Dr Haass, said he felt the time had come to halt prosecutions. “More than 15 years have passed since the Belfast Agreement, there have been very few prosecutions, and every competent criminal lawyer will tell you the prospects of conviction diminish, perhaps exponentially, with each passing year, so we are in a position now where I think we have to take stock,” he said. “It strikes me that the time has come to think about putting a line, set at Good Friday 1998, with respect to prosecutions, inquests and other inquiries.”

He added: “Sometimes the fact of an amnesty can be that that which was a crime ceases to be a crime. That wouldn’t be the position here, it would simply be that no criminal proceedings would be possible with respect to those offences.”

Mr Cameron told the House of Commons it would be “rather dangerous” to block possible future prosecutions. “I do think it’s important to allow Richard Haass to do his work about parades, about flags (the other two issues he is dealing with) and about dealing with the past,” he said. “Clearly the dealing with the past part is the most difficult of the three and the most difficult to unlock. “The second point I would make is that we are all democrats who believe in the rule of law, who believe in the independence of the police and prosecuting authorities, and they should if they are able to, be able to bring cases. “I think it’s rather dangerous to think that you can put some sort of block on that. “But of course we are all interested in ways in which people can reconcile and come to terms with the bloody past, so that they can build a viable future and a shared future for Northern Ireland.”

Stephen Gault, whose father Samuel was killed in the 1987 IRA Poppy Day bombing in Enniskillen, Co Fermanagh — an atrocity for which no-one has ever been convicted — said he was disgusted by the attorney general’s statement. “How dare he airbrush the innocent people who were murdered at the hands of terrorists to move things forward. I just think it’s totally disgusting,” he said.

Kate Nash, whose brother William was killed by British soldiers on Bloody Sunday in Derry in 1972, today challenged Dr Haass to reject any suggestion of an amnesty.

In the unscheduled encounter in the foyer of the City Hotel in Derry, Ms Nash made clear to the former diplomat her family’s opposition to the proposal. Afterwards she explained her anger. “What are they trying to do, draw a line under victims, draw a line under my brother? We are not going to let that happen,” she said.

A number of victims groups have also put on record their concern. Sandra Peake, of the WAVE trauma centre, said: “Many victims and survivors will interpret this as being told to be quiet so that the rest of us can get on with our lives. “It would be very hard to take that the people who made them victims, can now smile at them safe in the knowledge that as far as the State is concerned what they did has ceased to matter.”

It has not been universal criticism however. Mr Larkin found an unlikely ally in former Northern Ireland secretary Peter Hain - a politician he once took a court action against - who said while he did not favour an amnesty he thought the attorney general was right to start a debate on the issue.

“I think the attorney general said what needed to be said,” he said. “He was right to put his head above the parapet, because this issue is not going to go away.”

Sinn Féin president Gerry Adams claimed a de facto amnesty was already applied to members of the security forces. Mr Adams, who insisted a wider debate on the past was needed, said that, whatever approach was taken to the legacy of the conflict, the views of victims had to be central. “Their voices must be heard and respected and all victims must be treated on the basis of equality,” he said.The DUP, SDLP and TUV have all voiced serious concerns about the attorney general’s comments.

DUP Lagan Valley MP Jeffrey Donaldson said: “There is no nation in the free world today where murder is not a crime, you cannot say that murder is not a crime - it is. There are 3,000 unsolved murders in Northern Ireland and those families are entitled to the right to pursue justice.”

SDLP Assembly Member Alban Maginness said: “For Mr Larkin to say that his proposal does not constitute an amnesty is wrong.

“Mr Larkin does recognise that many will interpret it as one - that is because that is what it will effectively be. This would amount to a blanket amnesty and the SDLP do not believe that this would be acceptable.

“The international view, also held by the United Nations, is that general amnesty is not the correct way of proceeding in a post conflict situation.”

TUV leader Jim Allister said he was “appalled and angered” by the comments.

“Mr Larkin is not advocating amnesty for everyone, only for ‘trouble-related’ crimes; thereby endorsing the terrorist propaganda,” he said. “Murder is murder, is murder. It has no sell-by date. It didn’t have for the Nazis, who have still been pursued. Northern Ireland’s criminals must equally never be relieved of the threat of the long arm of the law catching up with them.”

Mr Donaldson, the DUP’s spokesman on victims’ issues, said Mr Larkin had not consulted the Northern Ireland Executive before making his comments. “He made it clear this is his own viewpoint and it’s not one that we share,” he told BBC Radio 4’s Today programme.

The proposal would set an “extremely dangerous precedent” not just in the UK but across the free world, he said.

“Effectively what it requires you to do is to say that if you form a terrorist organisation and you go out and you murder people in cold blood then one day you will be granted an amnesty for those crimes,” he said. “I don’t think the victims of 7/7 in London or 9/11 in New York would be up for an amnesty of this nature. There was certainly no amnesty for bin Laden so why should there be an amnesty for the IRA or for loyalist paramilitaries for the crimes they have committed?”

Former Police Ombudsman in Northern Ireland Dame Nuala O’Loan said a halt on prosecutions would constitute a violation of international law. Dame Nuala is currently working with barrister Richard Harvey, who was involved in the Bloody Sunday inquiry, on an independent review panel set up to monitor a major PSNI investigation into a string of Ulster Volunteer Force (UVF) murders in north Belfast. “We unreservedly condemn today’s suggestion by the Attorney-General for Northern Ireland,” Dame Nuala and Mr Harvey said in a joint statement.

The Independent Review Panel for the PSNI Investigation into Operation Stafford said it “unreservedly condemns” Mr Larkin’s uggestion.

Operation Stafford was previously known as Operation Ballast, which investigated allegations of RUC collusion in up to 10 murders by a UVF gang based in the Mount Vernon estate in north Belfast in the 1990s.

“To abandon prosecutions, inquests or inquiries into killings that took place before the Good Friday Agreement would constitute a wholesale violation of the UK’s legal obligations under domestic and international law,” it said. “It would cause untold distress to bereaved families and seriously undermine prospects for building confidence in the administration of justice, in particular in cases where there is evidence of potential collusion between elements in the security services and paramilitaries.

“A refusal to investigate and prosecute crimes of such severity would be a breach of the UK’s undertakings in ratifying the Rome Convention, potentially invoking the jurisdiction of the International Criminal Court.”