Any review of the events of Bloody Sunday should have an “overriding limitation” that no soldier should be placed in danger of legal action, Mo Mowlam told a cabinet colleague in 1997.

However, the then Northern Ireland Secretary also said she realised it would not be possible to deliver an “absolute guarantee” on such a limitation, newly released Government papers reveal.

Bloody Sunday was one of the darkest days in the history of the Northern Ireland Troubles.

Thirteen people were killed on the day in Londonderry, and another man shot by paratroopers died four months later.

Many consider him the 14th victim of Bloody Sunday, but his death was formally attributed to an inoperable brain tumour.

An immediate inquiry, led by then Lord Chief Justice Lord Widgery, was labelled a whitewash after it largely cleared the soldiers of blame.

There had been renewed focus on the 25th anniversary of Bloody Sunday in 1997 when Labour came to power.

Declassified files reveal that a civil servant prepared a briefing paper for Ms Mowlam on options for dealing with Bloody Sunday in May of that year.

It said: “There is no doubt that 25 years ago the events of January 30 1972 in Derry became a potent emblem of nationalist grievance. Time has not changed this.

“The 25th anniversary of Bloody Sunday this year was marked by a renewed and increased interest in the prospects of securing some kind of change in the Government’s position, either unilaterally or through the medium of a new inquiry.

“Expectations have been further increased by Labour’s victory, and there would be a political price to pay if nothing were done or said now.

“One interesting aspect of the anniversary was the breadth of opinion – including unionists in Northern Ireland and right-wing newspapers in Great Britain – calling for an apology.

“Because Bloody Sunday is a talisman there have also been people who claim that the right address to it by Government might have almost magical consequences – an apology for example, would be sufficient to produce an end to the IRA’s campaign.

“That thesis has not been tested, but it probably overstates the effectiveness of anything the Government could say.

“That said it is undoubtedly true that an apology (or something close to it) would have a tremendous impact, and if anything is to be done there is unlikely to be a more opportune moment.”

Options set out for the then NI Secretary included announcing a new inquiry or making an apology.

The note said: “There is a lot to be said for saying sorry.

“One problem with Bloody Sunday is identifying what there is to say sorry for. It is not clear.”

The briefing paper included potential wording for a draft apology.

The statement included: “I do not believe that the soldiers who fired the shots went there intending murder, but clearly it was wrong that people demonstrating for their civil rights were killed. I am sorry that it happened.”

A handwritten note beside the draft apology stated: “Too balanced”.

The following month Ms Mowlam wrote to the then Defence Secretary George Robertson stating her preference for announcing a new review into Bloody Sunday with an “overriding limitation”.

She continued: “The overriding limitation would be that no soldier or other Crown servant should be placed in jeopardy of legal action by whatever the reviewer might find or by what might flow from his findings.

“I realise it will not be possible to deliver an absolute guarantee on that override.”

A letter in response from Mr Roberston said: “I believe that a review would be fraught with difficulties and that the balance of risk against potential benefits argues strongly against it.

“I can, however, see much merit in an apology as an alternative, provided that, as you suggest, it expresses regret rather than ascribes blame.

“A heartfelt apology should, in my view, be the Government’s last word on the subject.”

After years of campaigning by victims’ families, then-prime minister Tony Blair ordered a new inquiry in 1998.

The Saville Inquiry concluded in 2010 that none of the casualties was posing a threat or doing anything that would justify their shooting and then-prime minister David Cameron apologised in the House of Commons, saying that the killings were “unjustified and unjustifiable”.

A committal hearing is set to take place in January to determine if there is sufficient evidence against a soldier accused of two Bloody Sunday murders for a case to proceed to Crown Court trial.