Around 300 republicans are claiming they were sent to jail on the back of confessions forced from them during interrogation.

Traditional Unionist Voice leader Jim Allister said no one could deny "occasional miscarriages of justice occurred" but the suggestion that hundreds of IRA terrorists, duly convicted, were actually all innocent was "preposterous".

Innocent people populate Ulster's graves, he added, not the ranks of former IRA prisoners.

And William Frazer of victims' group FAIR said he was disgusted that people – "most of whom were presumably happy to serve their sentences on IRA wings" – were now "rubbing salt into the wounds of the people whose loved ones they murdered and maimed".

Many ex-prisoners cannot find jobs, insurance or loans because of their convictions. They are also barred from entry to countries like the US.

Sinn Fein MLA Caral Ni Chuilin said: "A lot of men in Long Kesh were only there because they signed a confession extracted from them under extreme circumstances in places like Castlereagh and Gough.

"I am aware that there are a lot of people coming forward to build a case up.

"The issue about this is that this affected republicans and loyalists and people from unionist and nationalist working-class areas who were in the wrong place at the wrong time and ended up spending their lives in jail."

Earlier this year Danny Morrison, Sinn Fein's former publicity director, challenged his 1991 conviction for falsely imprisoning IRA informer Sandy Lynch a year earlier.

The Criminal Cases Review Commission recommended Mr Morrison's case go back to the Court of Appeal.

It is understood the prosecution service is unlikely to contest the appeal.

Michael Culbert, director of republican ex-prisoners' group Coiste, said there was no organised attempt to overturn convictions but added he was aware of a number of cases.

Mr Allister said: "Every terrorist conviction in Northern Ireland was the product of a due process with built in double judicial protection.

"Not only did a senior judge preside over every trial but every convicted terrorist – unlike 'ordinary' criminals – had an automatic right of appeal to three Judges in the Court of Appeal, and beyond, if appropriate.

"So every finding of guilt was well sifted judicially."

He added: "Let's remember the IRA murdered over 2,000 innocent people. Would they now have us believe that persons, other than those convicted, committed those and other heinous crimes.

"I know the IRA/Sinn Fein is on a mission to sanitise its past, and that for some such could be politically convenient, but their ranks are not the habitation of the innocent.

"The innocent populate the graves of Ulster, put are there primarily by IRA/Sinn Fein and thus it would be stomach-turning to see this campaign at re-writing history gaining any credence in the courts."