A Republican who famously coined the "armalite and ballot box" slogan has had his conviction for aiding and abetting the abduction of an IRA informer quashed by a Northern Ireland Court of Appeal.

But former Sinn Fein publicity director Danny Morrison says he will not accept British government attempts to stop him finding out the reasons for the overturning of his conviction.

On Friday Morrison and seven others had convictions relating to the 1990 abduction of Special Branch informer Alexander "Sandy" Lynch overturned by the Court of Appeal.

However, the reasons behind the landmark ruling have not been revealed.

In January 1990 Morrison was arrested at a house in west Belfast. In an adjacent house police found Lynch, who the IRA had held prisoner for two days.

At Morrison's trial he claimed to have gone to the house to arrange a press conference at which Lynch was to admit being a police agent. He was found guilty of aiding and abetting Lynch's false imprisonment and jailed for eight years.

At the trial, Lynch identified Freddie Scappaticci as the man in charge of his IRA interrogation.

Despite having had the house under surveillance, police failed to arrest Scappaticci, who went on the run in the Republic. He was questioned when he returned to Northern Ireland in 1992 but released without charge.

In 2003 Scappaticci publicly denied that he was the Special Branch agent known as "Stakeknife" and had tipped off police that Morrison would visit the house where Lynch was being held. He has since fled Northern Ireland and the media is banned from reporting on his whereabouts.

Earlier this year the Criminal Cases Review Commission (CCRC), which investigates alleged miscarriages of justice, referred Morrison's case back to the Court of Appeal. Unusually, the CCRC refused to give reasons for its decision.

On Friday the Court of Appeal quashed the convictions against Morrison and his seven co-accused. However British government barristers opposed any attempt to make the CCRC reasons public.

Outside the court, Morrison claimed that the security services were protecting Scappaticci.

"British intelligence knew all along what was happening because Sandy Lynch's handlers told him three days earlier that he was going to be questioned by the IRA about being an informer," said Morrison.

"I was lured to that house by Freddie Scappaticci because I intended to hold a press conference at which Lynch would admit to being an informer. The whole thing was a set-up from the beginning."

Insisting that he should now be entitled to know why his conviction has been overturned, Morrison added, "We were convicted in an open court amid a fanfare of bad publicity so I think it's only fair that the same consideration is given to the reasons why we were wrongly convicted."