A Democratic Unionist Party MP last night claimed that Sinn Féin politician Francie Molloy is a former British agent who is suspected of involvement in the murder of a former RUC reservist.
Mr Molloy is currently a deputy speaker of the Northern Assembly.
Speaking in the House of Commons in London, DUP MP David Simpson used parliamentary privilege to name Mr Molloy and to make a number of controversial claims about him being a suspect in the killing of Frederick "Eric" Lutton.
Mr Lutton, a 40-year-old father of two, and a cousin of Mr Simpson, was a former member of the RUC reserve who was shot dead on May 1st, 1979.
Mr Simpson, MP for Upper Bann, also alleged that Mr Molloy was well known to police for "sexual indiscretions" and had been consequently recruited as an informer.
He accused the Mid Ulster MLA of a "callous disregard for the lives of his neighbours" and said he was speaking out to "ensure that a story that needs to be told is told".
By making his claims in the Commons, Mr Simpson is protected from any possible legal action by Mr Molloy, who later accused the MP of abusing parliamentary privilege.
"Like his fellow unionist MPs, I have no doubt David Simpson, being a coward, will not repeat these allegations outside of Westminster," Mr Molloy said.
"Given this history I would expect all of us, the media included, to approach this latest stunt with extreme caution."
Opening a brief debate on policing in Northern Ireland, Mr Simpson said police believed Mr Molloy had a role in the murder of Mr Lutton, who worked as a caretaker for the National Trust and was killed as he got out of his car to lock the gates of their premises in Moy, Co Armagh.
The IRA claimed responsibility for the killing but no one has ever faced charges.
"While at the family home, investigating officers discussed the case in front of Mr Lutton's wife and his family," Mr Simpson told MPs. "They identified one, Mr Francie Molloy, as a live suspect having a role in the killing. They discussed the need to pursue a thorough investigation of Mr Molloy. To a man they agreed that this was a vital line of inquiry.
"All of this was discussed openly in front of his wife and his young family. Molloy was well known to the police, yet none of this was ever fully investigated."
He continued: "As well as being a suspect in the Lutton case and as well as being known to police, Francie Molloy was also well known, and this information is from the police, for a series of sexual indiscretions.
"He was caught by the security forces in a compromising position. As a result of this he was recruited as an informer for the police."
Mr Simpson claimed Mr Molloy had passed crucial information to the police which helped them "break open" the IRA's east Tyrone brigade. - (PA)