A former British agent who was at the centre of allegations of collusion between the security forces and Loyalist paramilitaries, has died of natural causes.

Brian Nelson worked with the Ulster Defence Association and was recruited by British military intelligence.

One of the assassination targets he compiled a dossier on was Belfast solicitor, Pat Finucane, who was shot dead by UDA gunmen in 1989.

Nelson's death comes as Metropolitan Police Commissioner, Sir John Stevens, prepares to publish a major new report on the killing and on claims of police and army conspiracy in the North with Loyalists.

Nelson was involved with a British army agency known as the Force ResearchUnit which was involved in gathering intelligence from Loyalists.

It has been claimed that the agency used him to prevent the UDA murdering ordinary Catholics and concentrate on targeting known Republicans.

However allegations persist that some warnings Nelson passed on to his handlers were ignored. Nelson had insisted that his security force handlers knew that the UDA had asked him to compile information on Mr Finucane.

These claims are at the heart of Sir John Stevens's investigation.

The ex-soldier, who was living at a secret location in England, suffered a heart attack two weeks ago. This was followed by a massive brain haemorrhage on Friday.