Parents of soldiers who died at Deepcut army barracks are considering going to the Police Complaints Authority over the handing of the inquiry by Surrey police force.
Relatives of the dead recruits refuse to believe it was suicide
The families say they have been appalled to find that Military of Defence police are involved in what they were assured would be an independent investigation.
Private James Collinson, 17, from Perth, died of a gunshot wound at the barracks and parents Jim and Yvonne insist it was not a suicide, as army investigations found.
James' death is part of an inquiry into the barracks currently being carried out by Surrey Police.
Mrs Collinson said she was furious to learn that army officials had been helping police with their inquiry.
"It has not been independent at all. The whole reason that there is a reinvestigation is because the army made such a shambles of the real investigation," she said.
"It effect, it has become the army investigating the army for Surrey Police."
Annabelle Ewing, MP for the Collinson's home city of Perth, said she intended to contact Surrey Police over the matter.
"I am disturbed to learn that MoD personnel have been involved in the Surrey Police investigation into soldiers deaths at Deepcut, even to the extent of taking witness statements."
She added: "This flies in the face of a assurances given to the families that this would be exclusively a police enquiry and, these actions clearly compromises the integrity and independence of the Surrey Police Investigation.
"This underlines the need for a full independent public inquiry into these tragic and unexplained deaths at Deepcut barracks.
"That is the only way that the truth can finally be uncovered."
A spokesman for Surrey Police said: "It is essential that the investigation has the benefit of expert advice on the working practices of the army.
"Surrey Police are completely satisfied that they have acted in a professional manner."