AN INVESTIGATION is under way after a member of Prime Minister Tony Blair's armed guard accidentally fired a shot while on duty.

The police marksman had finished his shift protecting Mr Blair, who was at Myrobella, his residence in Trimdon Colliery, in his Sedgefield constituency in County Durham.

The constable fired a round inside the armoury at Durham Police headquarters, on the outskirts of Durham City, as he went through the procedure of making his weapon safe.

No one was injured as the bullet ripped into a safety curtain at the opposite end of the firing range.

The incident follows an embarrassing blunder last year in which a shot was fired by an officer startled by a pigeon while on duty outside Myrobella.

The constable involved in the latest mishap involving the unit is back on protective duties and has not been disciplined.

Durham Police Assistant Chief Constable Ron Hogg defended his officer.

He said: "I can confirm a weapon was accidentally discharged within the armoury at Durham Police headquarters by a member of the armed protection team.

"Because procedures were being carefully followed, it harmlessly hit the safety curtain at the opposite end of the range.

"At no time was anyone in danger. While the incident continues to be the subject of an internal investigation, it was not felt necessary to order a review of safety procedures or suspend the officer.