The Royal Institute of International Affairs, known as Chatham House, said that Britain's support for the US did not mean it was an equal partner but a "pillion passenger compelled to leave the steering to the ally in the driving seat".
The think-tank concluded that "the UK is at particular risk because it is the closest ally of the United States, has deployed armed forces in the military campaigns ... in Afghanistan and in Iraq, and has taken a leading role in international intelligence, police and judicial co-operation against al-Qa'ida and in efforts to suppress its finances," it said.
Chatham House warned that Iraq had created difficulties for the UK and the coalition. "It gave a boost to the al-Qa'ida network's propaganda, recruitment and fundraising, caused a major split in the coalition, provided an ideal targeting and training area for al-Qa'ida-linked terrorists, and deflected resources that could have been deployed to assist the Karzai government [in Afghanistan] and bring Bin Laden to justice," it said.
The co-authors of the report, Frank Gregory of Southampton University and Paul Wilkinson of St Andrews University, said that although Britain's experience in handling Irish-related terrorism had helped co-operation between agencies, there were still "many worrying gaps" - for example, no immediate prospect of compatible radio communications among the emergency services.
"Obviously London is a high-profile target zone, but it should be borne in mind that al-Qa'ida terrorists (and IRA terrorists) have never confined themselves to attacks on capital cities," it said.
Chris Smith, a former Labour cabinet minister, said Britain's support for the Iraq war had "probably" made it more vulnerable to attack, but that it was wrong to make a direct connection to the London bombings.
The Government faced more embarrassment when it emerged that it is trying to block the publication of a bookby Sir Jeremy Greenstock, the UK ambassador to the United Nations at the time. He describes the US decision to go to war as "politically illegitimate" and says UN negotiations "never rose over the level of awkward diversion for the US administration".
The book, The Cost of War, also discloses private conversations that Sir Jeremy had with Tony Blair and the Foreign Secretary, Jack Straw.Reuse content