Senior ministers dismiss these critics with a predictable disdain: "No surprise about Galloway ... Typical of Clare." "Poor old Kennedy misread the public mood." "The bombs in London are nothing to do with Iraq. Disgraceful that anyone could suggest otherwise." "Bad taste at a time when we must unite."
But now they face a more substantial challenge. This week's authoritative report from the think-tank Chatham House is not so easily swept to one side. It changes the tone and substance of what was becoming a deceptively tame debate.
The report argues that Britain is at greater risk of a terrorist attack because of its close association with the US. It also asserts that the war against Iraq increases the capacity of terrorists to strike: "The conflict 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 and assistance that could have been deployed to assist the Karzai government in Afghanistan and to bring Bin Laden to justice."
When established think-tanks disturb, ministers reveal their unease by protesting too much. The Defence Secretary, John Reid, got more worked up than he needed to do as he was probed fairly on the BBC yesterday about the report. The normally calm Foreign Secretary, Jack Straw, virtually screamed a soundbite of protestation into a passing camera.
Mr Straw and Dr Reid have their case prepared. We will hear often in the coming weeks about the countries that suffered terrorist attacks before the war against Iraq. Downing Street published a list last week.
We will hear also a theoretically irrefutable argument from government that it would be cowardly to turn away from a conflict out of a fear of retaliation. Finally ministers will argue that terrorists strike in Iraq precisely because the war has been a success in establishing democracy. The stakes are high. The terrorists must not be allowed to prevail.
None of these superficially strong arguments address the criticisms in the Chatham House report. It is true that some countries were attacked before the war against Iraq. No one disputes this. The argument in the Chatham House report is that the conflict has acted as a recruiting agent and training ground for more terrorists. The terrorists posed a threat before the war. They pose a much bigger one now.
Britain's vulnerability is not a reason in itself for withdrawing support from the United States, but the cause of the alliance must determine whether the risks are worth it. In this case, the cause has led to a greater terrorist capacity, a diversion of attention away from Afghanistan and a fractured international community.
In his Commons statement immediately after the opening of the war against the Taliban, Mr Blair stated that Afghanistan would never be neglected again and that nothing would be done to threaten the global coalition against the terrorists that had grown in the days after 11 September 2001. The war against Iraq broke both those pledges.
To argue that the terrorists' insurgency in Iraq is a form of vindication for the war is especially perverse. President Bush and Mr Blair were explicit in insisting that the war was necessary to address the threat posed by terrorism. As a result of the war the threat is greater.
As the months go by, the political charges in relation to the war do not change. They become more tragically pertinent. They do so as more light is shed on the build-up to the conflict and the number of those close to Mr Blair who expressed their doubts.
We already knew that the Foreign Secretary, Jack Straw, had worries about the political consequences of a war. After the Crawford Summit in the spring of 2002 between Mr Blair and President Bush, the Foreign Secretary warned about the impact of the war on the Labour Party and beyond in a memo that was subsequently leaked. Mr Blair insists that he made no commitments, even provisional ones, in relation to Iraq at the Crawford summit. So why did Mr Straw feel compelled to write the memo immediately afterwards?
Now the UK Ambassador to the UN during the build-up to the conflict, Sir Jeremy Greenstock, describes the war as "politically illegitimate" and the aftermath as "dissipated in poor policy analysis and narrow minded execution". His comments are made in a book the Government is trying to prevent from being published.
I am told that the former head of the armed forces, Sir Charles Guthrie, advised Mr Blair that the war would be destabilising. We know that Britain's Ambassador to the US at the time, Christopher Meyer, looked on warily, accusing Mr Blair of failing to exercise candour with President Bush in private let alone in public.
What is happening in Iraq now and to other countries, including Spain and Britain, should therefore come as no surprise at all to President Bush and Mr Blair. The intelligence agencies warned in advance that the war would increase the threat posed by terrorists. Mr Blair's closest advisers, from his Foreign Secretary to various senior diplomats, had their different doubts. It is becoming increasingly clear that Mr Blair decided to back the war against Iraq in spite of warnings from from a range of close colleagues and advisers. The recent bombs in London, Turkey and of course Baghdad call this judgement into question once more.
Most Labour MPs are keeping their heads down at the moment, but quite a few agree with the report from Chatham House and express private amazement that the issue did not surface in the immediate aftermath of the bombings in London. This is the political significance of the report. It breaks the near political silence and yet speaks for a significant number of MPs and indeed ministers. In that sense the timing for the government could not have been worse.
The Government has a right and arguably a duty to seek new legislative powers in the face of the threat posed by terrorists. I put the case for stronger anti-terrorist legislation before the bombings, when the Conservatives and Liberal Democrats were keeping MPs up all night to disrupt the Government's plans. Mr Blair deserves praise also for the way he has encouraged leaders of the Muslim community to become part of the political response to the London attacks. But his reluctance to accept that Britain's foreign policy is a key factor in the current appalling tension limits his ability to lead us towards a less scary future.Reuse content