A former British agent in the IRA believes the gun used in an IRA assassination attempt on him was one of those allegedly smuggled from the US by Sean 'Spike' Murray.
And he suspects that Sinn Féin intervened politically to ensure that two men being questioned by detectives about his attempted murder were released without charge.
Martin McGartand says there has been "a massive cover-up" surrounding the semi-automatic pistol used in the 1999 attack.
Speaking from a safe house in England, he said: "This is all about protecting the IRA. Time and time again, police have concealed information about my attempted murder.
"Only after persistent questioning have I been told the gun used was a clean weapon and there is 'an international angle' to the case.
"I've now asking the Police Ombudsman to find out if the gun was among those smuggled from America by Spike Murray. It's time the PSNI and Northumbria Police came clean."
A BBC Spotlight documentary last week alleged that Murray was involved in smuggling more than 400 guns from the US between 1995 and 1999.
Some of these weapons were allegedly used in the 1997 murder of two policemen in Lurgan and the killing of leading Belfast dissident republican, Joe O'Connor, in 2000.
McGartland was shot six times after he got into his car outside his home in Whitley Bay, Tyneside, in June 1999. A gunman appeared at the window and fired into the vehicle which was parked at the back of the house.
Another gunman had been positioned at the front of the house in case McGartland left that way. His life was saved by neighbours who used cling film to stop the blood flow from his wounds.
In August, a man walking his dog along the River Tyne found two guns hidden in undergrowth. One was the Czech-made Luger pistol used in the attack. The other was the hand-gun apparently carried by the second IRA man.
McGartland said: "Northumbria police never told me these guns were found. I only discovered that when a police man guarding me let it slip in conversation.
"The police disgracefully still won't even say the IRA was involved. In fact, they've gone to great lengths to distance the IRA from my shooting.
"Police have the gunman's DNA but when I ask if there's a suspect they want to interview or if they'd done familiar DNA database searches to see if they've a close match, they wont tell me."
Both guns were sent for examination to the Weapons and Explosives Research Centre in Northern Ireland. McGartland is demanding all information from this.
In November 1999, Northumbria police questioned two republicans, including Harry Fitzsimmons from Belfast, about conspiring to murder him.
McGartland said he was told police had enough evidence to charge them and newspapers ran stories that they were due to appear in court.
Sinn Féin's Gerry Kelly issued a strong statement demanding Fitzsimmon's "immediate release", saying the police's actions ran "counter to the peace process and can only cause difficulties for those attempting to break the political impasse".
Detectives subsequently released both men. McGartland said: "We know now that following a phone call from Gerry Adams in March 2007, Downing Street tried to get two republicans being questioned about an attempted murder in Co Tyrone released. I want to know if similar interference occurred in my case."