Liberal Democrat leader Charles Kennedy has opened his party's annual conference with a call for Tony Blair to apologise for mistakes over Iraq.
Mr Kennedy says he is looking forward to lively conference debates
Addressing a rally in Bournemouth, Mr Kennedy called the war a "tragic folly" and the "biggest foreign policy error" since the Suez crisis.
It had left the UK's foreign policy reputation "in tatters" and eroded trust in politics in general, he said.
"At the very least prime minister just say sorry," Mr Kennedy told delegates.
Mr Kennedy said: "Our reputation as a steady and stable force in international affairs is in tatters.
"We are no longer sure we can trust our intelligence services.
"We recoil from the loss of trust in government lawyers, former judges, senior civil servants - who have been sullied by entanglement with this mistaken war."
0900: Formal opening
0920: Debate on reducing the risk of terrorism
1100: Speech by Baroness Williams of Crosby, party Leader in the Lords.
1200: Speech by party Deputy Leader Sir Menzies Campbell
1415: Speech by Treasury spokesman Dr Vincent Cable
1530: Question and answer session with party Leader Charles Kennedy
He said it was "too late to turn back the clock," on much of the damage, but the prime minister could at least apologise for his mistakes.
"Prime minister, why not just, even now, admit you got it wrong? Apologise? Say sorry for the damage you have done, the anguish you have caused, the wrongs that you can never now right?," Mr Kennedy said.
Earlier, at a press conference, Mr Kennedy said Mr Blair had "one opportunity left, when Parliament reassembles, to make a full and frank disclosure" of the run up to war.
In particular, the prime minister still had not answered the question of whether he had told US President George W Bush that Britain would be with the US in an Iraq war "come what may" before Parliament voted on the issue, Mr Kennedy said.
In a conference speech on Monday morning the Lib Dem outgoing leader in the Lords, Baroness Shirley Williams will say the Iraq war is the "greatest blunder since Suez."
"The government cannot move on until it admits this.
"The government neglected the war on terror for a war on Iraq - a war of its choosing," she will say.
The consequences of that war was a lawless Iraq that is slipping into chaos, she will say, adding the "terrorist menace" had grown not declined.
In a lunchtime speech, Lib Dem deputy leader Menzies Campbell will reiterate Mr Kennedy's calls for the prime minister to apologise.
He will demand a rethink of US-UK relations, saying the alliance would work better if Britain was candid and independent.
He also warns a Democrat-led US administration would not change the substance of US foreign policy.
The Lib Dems come into their conference on the back of strong showings in recent by-elections and local council polls.
Mr Kennedy said the Lib Dems were now "one of three main equal partners" in British politics, "to an extent that has not been seen for 20 years, arguably even 30 years".
And he denied that by focusing on Iraq, he was in danger of turning his party into a "one-trick pony".
Iraq symbolised a wider breakdown in trust in Labour and politics in general, Mr Kennedy said.
Conservative defence spokesman Nicholas Soames insisted it was right to topple Saddam and to "liberate" Iraq but he was critical of post-war planning which he branded "chaotic".
In a draft manifesto launched earlier last week, the Lib Dems pledged to, among other things, scrap tuition fees, introduce free personal care for the elderly and replace the council tax with a system of local taxation.
These policies would be paid for by introducing a 50% tax rate on those earning over £100,000 a year.
Mr Kennedy said seven out of 10 people would be better off with the Lib Dems' planned system of local taxation replacing the council tax.
He told the BBC's Breakfast with Frost: "The majority within that proportion of winners will be pensioners and single householders."
He added: "Younger people will benefit from the fact that if their children are going to become university students... they won't be saddled with the colossal amounts of debt that they are going to incur.
Right wing policies
Mr Kennedy also defended the fact that there was only a small mention of Europe in its pre-manifesto document, suggesting that voters knew what Lib Dem policies were on this issue following the European elections in June.
But there is a debate amongst Lib Dem MPs about whether they should adopt more right-wing policies.
Some think such a change in direction would attract more Conservative votes in the party's most winnable seats.
Mr Kennedy believes recent by-election and council successes show the party can compete in both Labour and Tory heartlands.