The UK needs to spell out when armed guards can use potentially lethal force against pirates, a new report says.

The foreign affairs select committee applauded Prime Minister David Cameron’s recent u-turn on the use of armed security teams on board UK-flagged vessels, but said guidelines on the legal use of force “lack critical detail”.

"The government's guidance on the use of force, particularly lethal force, is very limited and there is little to help a ship's master make a judgement on where force can be used,” committee chairman, Conservative MP Richard Ottaway, said.

"The