Afghanistan’s police are poorly trained, plagued by drug addiction and infiltrated by the Taliban “at every level”, a former British soldier from Portadown has said.

The Afghan National Police (ANP) is actually a militia made up of local men whose allegiances are to their tribes rather than the national or local governments, according to Captain Doug Beattie.

Mr Beattie, who worked with the ANP during tours of Afghanistan in 2006-07 and 2008, said Afghan police officers were often paid off by insurgents.

But he suggested that Tuesday's horrific shooting, in which five British soldiers were killed by a rogue Afghan policeman, could have been sparked by a cultural misunderstanding.

“The Grenadier Guards have only just arrived there. They are getting to know the Afghan police,” he said.

“It could be somebody has said or done something and there's a general grievance.

“It could be that they have offended him without realising it, with them being new in country.”

Mr Beattie has had his own run-ins with the Afghan police — he believes an ambush of his unit in Garmsir in Helmand Province in 2006 was set up between the Taliban and the ANP.

He also alleged that a former chief of police in Helmand was caught talking directly to the Taliban on his personal phone on several occasions.

“It is absolutely right to say that the Afghan police are infiltrated by the Taliban at every level, from the very lowest to the very highest,” he said.

“Fears about the police are really well founded and they have been known about since 2006.

“There are a number of real problems. They're not really trained properly.

“They're really a militia, a tribal police whose allegiances are not necessarily to the government or even to the provincial governor. It is normally to their village or tribe or the area they come from.

“Because they're militia they can be bought and paid off at will. If they don't get enough money they're quite happy to be paid by the insurgency.”