A committee of MPs has concluded that invading Iraq has done little to reduce the terrorist threat to Britain.

The Commons foreign affairs committee said in a report yesterday that the overthrow of Saddam Hussein could have "impeded" efforts to capture al Qaeda fugitives including Osama bin Laden.

"The war in Iraq might in fact have impeded the war against al Qaeda," the report said.

"In spite of some notable progress, al Qaeda continues to pose a substantial threat to British citizens in the United Kingdom and abroad.

"We cannot conclude that these threats have diminished significantly, in spite of 'regime change' in Iraq and progress in capturing some of the leaders of al Qaeda."

The Foreign Office confirmed yesterday that a British man had been arrested in Morocco on suspicion of being a member of the Islamic group that killed 44 people in a suicide attack in Casablanca last May.

The number of Britons held in Guantanamo has risen to 12, the Guardian has reported.