Some of the darkest secrets of the IRA and loyalist paramilitary killings during the Troubles in Northern Ireland are set to be revealed in the coming years as direct participants' accounts, under lock and key in the US, are released.

The accounts were given to academic researchers from the prestigious Boston College on strict condition that they could only be released with the express permission of the ex-terrorists or in the event of their deaths.

The college's Irish Institute has spent the last six years and millions of dollars paying researchers to interview the former IRA men and loyalists.

Two sets of accounts from the archive are set to be published early next year by Faber & Faber in a book provisionally entitled "Voices from the Grave".

The accounts are by Brendan "Darkie" Hughes, one of Gerry Adams' closest associates in the IRA in Belfast in the Seventies and Eighties, and loyalist David Ervine. Hughes, who suffered ill-health since his prolonged hunger strike in 1980, died in March last year.

David Ervine, who died in 2007, was one of the top bombmakers of the Ulster Volunteer Force and his account could shed light on the 1974 Dublin and Monaghan bombings, in which 33 people died.

Boston College does not comment on the archive but it is understood that dozens of ex-terrorists agreed to commit accounts of their actions.

Speculation has been rife in republican circles that the account by Brendan Hughes could cause huge embarrassment. Hughes and Adams were very closely associated in the early years of the Troubles. He fell out with Adams and was openly critical of the IRA's decline into criminality and Sinn Fein's acceptance of the Good Friday Agreement.

Hughes was part of the west Belfast IRA responsible for the abduction and murder of widow Jean McConville in December 1972, claiming she was an informant for the British Army.

Mrs McConville's daughter, Helen McKendry, said: "That's the lie they put out to cover up what they did. They even told people that I was a runner for my mummy taking stuff to Hastings Street (the local police station then doubling as an army base)."

She said she had asked Adams directly what had happened to her mother but he had never given any answers -- he still denies even having been in the IRA. "When Adams came to my house, he showed up at the door. He said he needed to go to the toilet. It took him 15 or 20 minutes to come out.

"He put out his hand for me to shake it but I wouldn't. He could not look at me. When I said I didn't think what they were saying was right, all he said was he would look into it. He couldn't wait to get out of the house."

Hughes almost certainly knew the truth of what happened to Jean McConville, whose body was eventually found at Templetown Beach on the Cooley Peninsula, Co Louth in 2003. He was imprisoned along with Adams in 1973, but he escaped six months later.

He was re-arrested in 1976 when police raided a house in south Belfast and found a bomb factory. He was "officer commanding" of the IRA prisoners and led them into the three-year "blanket" and "dirty" protest that preceded the first hunger strike in 1980, refusing food for 53 days.