Police admitted today that errors were made in investigating the death of a North-East soldier, and three other privates, who died in suspicious circumstances.

The head of Surrey CID, Detective Chief Inspector Craig Denholm, who has been drafted into the investigation from the Milly Dowler inquiry, said that more detailed post-mortem examinations should have been carried out.

The news comes as police exhumed the body of James Collinson, 17, of Perth yesterday as part of a ongoing investigation into the deaths at Deepcut barracks in Surrey.

A second post-mortem is to be carried out on the soldier who was discovered dead with a single gunshot would to the head at the barracks in March this year.

Senior police officials have now admitted that highly-qualified Home Office pathologists, normally called in after suspicious deaths, should have carried out the examinations instead of the less-experienced consultant pathologists that were used.

Det Chief Insp Craig Denholm said: "With the benefit of hindsight, we would have undertaken special post-mortems on all four of these individuals."

The move to exhume Pte Collinson's body has been welcomed by the parents of Private Geoff Gray, formerly of Seaham, County Durham.

The couple had advised James Collinson's parents not to have their son's body cremated, in case further tests needed to be carried out.

Investigations into Geoff's death have been hindered because he was cremated before suspicions about his death arose. His ashes are kept at the family grave in Princess Road cemetery in Seaham.

Speaking last night, Geoff Gray senior, said: "For James's body to be exhumed is good in our case. Even though we can't have Geoff's body exhumed, if they do find something with James, we can stand up and say, 'this should have happened to my son. Why did this not happen to my son?'

The Grays have been frustrated by the police investigation into Geoff's death.

Leading forensic expert Frank Swann, who spent two months carrying out a number of tests, does not believe that Geoff Gray killed himself, but detectives will not take his evidence on board.

Mr Gray said: "The police have got their own ballistics experts and they are not going to take Frank Swan's findings on board."