Charles Kennedy wants his party to become the main opposition

The Liberal Democrat leader reminded conference that this week was the first anniversary of the government's controversial September dossier about the threat posed by Iraq's weapons of mass destruction.

With the Hutton inquiry cross-examining Defence Secretary Geoff Hoon over his role in the naming of Dr David Kelly, it was vital that ministers did not simply "reiterate what went before".

"The message from the country to the government and to Tony Blair in particular is that simply going over old ground again with people defending their entrenched positions simply will not do given what the country now knows," he said.

"If Parliament had known what the country now knows the very vote which led us into this unnecessary conflict could and should have had a very different outcome indeed."

We have to be more professional and more strict in our entire approach as a party Charles Kennedy Time right for Lib Dem surge? Lib Dems see off monarchy vote

Fresh from their victory in last Thursday's Brent East by-election, the party was clearly in good heart as Mr Kennedy thanked the Lib Dem who ran against Iain Duncan Smith at the last general election for not winning.

He was even asked who he would vote for in Pop Idol and Fame Academy.

But in the main there were serious questions about serious issues such as reigniting people's enthusiasm for politics and delivering effective public services.

With his jacket off - he proudly showed off its Liberal Democrat yellow lining - Mr Kennedy seemed determined to live up to his earlier message to be "joyful" rather than "triumphant".

He is encouraging his party to focus on winning a range of votes next summer, including ballots for the European Parliament, local councils and London mayor.

EU constitution

On Monday the conference began to flesh out a range of policies aimed at boosting their chances of becoming the main opposition, rather than the Tories.

They will debate many environmental issues, including rainforests and GM crops.

Mr Kennedy has made it clear the old ideas of co-operating with Labour have now "withered away", and the party will in future go it alone.

Delegates also endorsed a statement on the proposed EU constitution, written by Mr Kennedy.

In an introduction to a document on the European Parliament elections, the Lib Dem leader supported the changed constitution, which has been drawn up to ease the EU expansion from 15 to 25 members.

He wrote: "[The] proposals already reflect our thinking in significant measure, and we look forward to working with others to help secure their implementation by national governments across the union."

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The document stated that "any major constitutional change that significantly affects the powers of the British people and their elected government should be subject to a referendum of the British people".

It added: "This means that if a future draft European constitution proposes major changes, there should be a referendum."

Later in the week, delegates will discuss other issues including abolishing council tax and student tuition fees, in an attempt to capitalise on the government's current difficulties.

On Sunday the party saw off potentially embarrassing proposals from its youth wing for a referendum on replacing the Queen as head of state.