The presence of British troops is now "part of the problem" in Iraq, Liberal Democrat leader Charles Kennedy is to say in a speech.
In one of his most personal attacks on Tony Blair's handling of the war and its aftermath, Mr Kennedy will accuse the Prime Minister of being "in denial" about the fact that most Iraqis now view UK and US soldiers as occupiers, not liberators.
And he will demand to know: "When can our troops come home?"
In his keynote speech to the Liberal Democrats' annual conference in Blackpool, Mr Kennedy will attempt to counter accusations of weak leadership by taking a tough stance on both Iraq and anti-terror legislation.
On Iraq, he will say that the PM is allowing his "pride" and his "blind support" for US President George Bush to stand in the way of a solution involving the phased withdrawal of British troops.
And on terror, he will accuse Mr Blair of "playing politics" in his response to the July 7th bombs in London, by bringing forward illiberal legislative proposals without consulting opposition leaders.
Following Wednesday's warning from home affairs spokesman Mark Oaten that the Lib Dems will not offer the Government a "blank cheque" on anti-terror laws, Mr Kennedy will unequivocally state that the party "shall not accept what is on offer" from Home Secretary Charles Clarke.
Accepting Mr Clarke's proposals for an offence of glorifying terrorism and a three-month detention period without charge for terror suspects would mean "surrendering our fundamental rights", he will say.
Mr Kennedy's speech comes just three days after the dramatic events in Basra, where British troops went to the rescue of two special forces soldiers handed over to militiamen by Iraqi police.
Senior aides denied that he was being unpatriotic by suggesting that the troops' presence in the country is fuelling the unrest which has resulted in thousands of deaths over the past two years. He had been supportive of the troops throughout their deployment, said a spokesman.
In a furious attack on Mr Blair's efforts to neutralise criticism of his conduct over Iraq, the Lib Dem leader will say: "However hard this Government tries, it cannot 'move on'. You cannot move on when the Prime Minister remains in denial. You can't move on when people are dying every day. And you cannot move on when our British troops are still there in the firing line. The Government must confront the fact that the presence of British and American troops in Iraq are a part of the problem.