Democratic Unionist MP Peter Robinson says he has received new information about the murder of loyalist Billy Wright.
Peter Robinson called for a full public inquiry into Wright's death
The East Belfast MP told the Commons on Thursday he was anonymously sent what he believed to be the police file on Wright's murder.
Wright, 37, leader of the splinter group the Loyalist Volunteer Force, was shot dead while serving a sentence in the Maze prison on 27 December 1997.
He was killed by three members of the republican paramilitary Irish National Liberation Army.
Mr Robinson told MPs the document reported that prison authorities knew a murder bid would take place and showed Wright's death could have been prevented.
Mr Robinson called for a full public inquiry into Wright's death.
In response, Northern Ireland Security Minister Jane Kennedy said the government's view was that a public inquiry was unnecessary as the death had been adequately investigated.
In March this year, the High Court in Belfast dismissed an application by Wright's father, David, to gain access to the police's file on the killing.
Billy Wright was murdered in the Maze Prison in December 1997
Mr Justice Kerr dismissed the 70-year-old's application for a judicial review of the decision by former Chief Constable Sir Ronnie Flanagan to refuse access to the file.
The judge said Mr Wright had been concerned that there may have been collusion on the part of the authorities that facilitated his son's murder.
Mr Justice Kerr said he was satisfied that an investigation compatible with human rights legislation had not yet taken place.
A judge appointed by the British and Irish Governments to investigate killings involving allegations of collusion by the security forces with paramilitaries on both sides of the Irish border has finished his assessment of Wright's murder.
Retired Canadian judge Peter Cory announced in April he was halfway through examining six controversial cases including the murders of the lawyers Pat Finucane and Rosemary Nelson.
The government is committed to holding a public inquiry into any of the deaths if the judge recommends it in his final report, which is expected in the autumn.
Mr Justice Cory's recommendations on these two cases are being kept at an unspecified location in Canada along with his findings on the Wright case.
In May 2002, the Northern Ireland Human Rights Commission called for an independent, international inquiry into Wright's murder.
The commission said that, having examined all the facts of the case, it believed such a process was the most likely way to establish what happened.
Wright founded the LVF after splitting away from the mainstream paramilitary Ulster Volunteer Force.