Thomas Keys served with the Parachute Regiment in Sierra Leone

Thomas Keys, whose family live in Llanuwchllyn near Bala was killed last summer whilst manning a small police station in al-Majir al-Kabir, 120 miles north of Basra.

The Lance Corporal's father, Reg Keys, says he has personally uncovered a document which he claims show the soldiers should not have been in the town where they died.

His MP Elfyn Llwyd has now written to Tony Blair asking him to intervene.

Mr Keys claims he has letters which show that the Army broke its word in a deal with Iraqi citizens in the town.

It is appalling that Mr Keys has felt it necessary to carry out his own investigation into his son's death Elfyn Llwyd MP

Following his personal investigation, documents have been uncovered which show an agreement was brokered by a senior British Army member and town elders.

The document, dated 23 June 2003 would seem to suggest that British forces would not be sent into the town for two months following fierce fighting.

The deal was broken within 24 hours of signing and Mr Keys believes this negligence directly led to the death of his son and five colleagues on 24 June.

Lance Corporal Thomas Keys was one of six military policeman killed in the incident.

Elfyn Llwyd, Plaid Cymru MP for Meirionydd Nant Conwy said he has written to Tony Blair and included a copy of the document referred to by Mr Keys.

"It is appalling that Mr Keys has felt it necessary to carry out his own investigation into his son's death," he said.

Mr Keys has launched a personal investigation into his son's death

"Indeed it was through his own contacts in Iraq that he got hold of a copy of this document.

"The official investigation by the Royal Military Police Special Investigation Branch is dragging and this is not the first time I have asked the Prime Minister to intervene in the case.

"I sincerely hope he takes my request seriously this time and acts upon it," he added.

However, an Army spokeswoman has said that they are already aware of the documentation in question.

"It is part of the SIB investigation and is with the board of inquiry," she said.

"We are unable to comment further on forensic evidence."

The six policemen killed were serving with 156 Provost Company.

They were ambushed and attacked by an angry mob believed to be loyal to Saddam Hussein.

They took cover in the police station but were surrounded by the gunmen.

The deaths caused revulsion in Britain following claims they were not killed in open combat, but executed by their attackers.

It was the largest single loss of life suffered by the British Army in one day since the first Gulf War in 1991.