Claims that the UK has committed war crimes against Iraqi civilians are being examined by the International Criminal Court after complaints by a panel of legal experts.
In a letter seen by The Independent on Sunday, the chief prosecutor of the ICC in The Hague has described the war crimes allegations as "one of the most significant" cases he has seen, and were being given "deserved weight" by his investigators.
Luis Moreno Ocampo, the chief prosecutor, indicated that his office has now begun the formal process of gathering evidence about the claims and is now expected to ask the Government to explain its military strategy in Iraq.
Sir Menzies Campbell, the Liberal Democrats' foreign affairs spokesman, said the move would cause "profound concern" for the Government. Adam Price, the Plaid Cymru MP and one of the most prominent critics of the war, added: "This is a highly significant development."
The allegations against the Government were submitted earlier this year by a lawyers' group called PeaceRights, based at the University of Warwick, in a dossier written by a panel of eight leading experts in international law.
The panel alleged that Britain had illegally used cluster bombs in civilian areas and illegally targeted power stations, depriving civilians and hospitals of water supplies and electricity. They also allege that British use of depleted uranium armour-piercing shells was negligent.
Sir Menzies said the decision to study the allegations was particularly worrying for Tony Blair's government because the UK had been one of the main driving forces behind setting up the ICC. "The UK's conduct of warfare will now be open to acute review, and British conduct and policy will be judged by higher standards than ever before," he said.