Nick Clegg urges faithful to their 'biggest fight'
The party unveiled its campaign slogan ahead of the conference
The Liberal Democrats are in for the biggest fight of their political lives, leader Nick Clegg has told the party's spring conference.
He told delegates in Birmingham the "election is still wide open".
Mr Clegg's rallying speech comes as his party announced their campaign slogan as: "Change that works for you. Building a fairer Britain".
Labour's election slogan is "a future fair for all" while the Tories have said 2010 will be a "year for change".
Mr Clegg told delegates: "On Monday morning I want you to get out there and go for broke in what will be the biggest fight of our political lives."
He said the electorate "haven't made up their minds".
Mr Clegg said: "This government knows it's come to the end of the road. The Tories know people have started to see through them.
"And voters know the Liberal Democrats offer something different."
Politics 'still dirty'
His speech follows the announcement of the party's campaign slogan, which combines themes of the slogans of both Labour and the Conservatives.
Mike Sergeant BBC News political correspondent, Birmingham
The Liberal Democrat slogan reflects the party's enduring dilemma. Which way to face? "Change that works for you" is clearly the bit aimed at the Tories. "Building a fairer Britain" takes on Labour more directly - as the Lib Dems try to assume the mantle of the party that will tackle inequality.
The slogan may be clunky, but it seems appropriate given the big question being asked on the sidelines of this conference: Would the Lib Dems prefer a coalition with Labour or the Tories?
It may well be that the election isn't in fact as close as some polls suggest.
But Nick Clegg says there will be "no back-room deals". Any hint that he's edging closer to either Labour or the Tories could fatally undermine local campaigns in tight marginal seats. The task for the leadership will be to sound serious about the possibility of power. Anything more specific risks opening up serious divisions in a party getting ready for a very tough fight on two fronts.
Senior Lib Dem MP Danny Alexander said only his party could deliver both pledges.
Mr Alexander said: "The Labour Party has let people down, they failed to make Britain fair, failed on the economy, failed to protect our environment and they failed to clean up politics.
"Everybody knows that the Conservatives will only make things better for those at the top. The Liberal Democrats are different because we are the only party that will deliver a fairer Britain and bring change that works for you."
But Labour and the Conservatives both pointed out the similarities to their own slogans.
A Labour spokesman said: "We all know Nick Clegg tries to be all things to all people, but with this election slogan it's really getting ridiculous.
"Next they'll be changing their emblem to a yellow bird sitting in a badly drawn green tree with a red rose hanging out of its beak."
A senior Conservative Party source told the BBC the Lib Dem slogan was "wishy-washy" and "a bit of one thing and another" adding: "Just what you'd expect from the Lib Dems."
Meanwhile, it was announced that former Conservative MEP Edward McMillan-Scott was joining the Lib Dems - he had been expelled from the Tories in a row about their new grouping in the European Parliament.
Mr Clegg will make his keynote speech at the conference on Sunday.
He has found himself facing questions about what his party - the UK's third biggest - will do in the event of a hung parliament after the general election - widely expected to be held on 6 May.
On Friday, he repeated his message that he would pose four tests to either Labour or the Conservatives if they sought his party's support.
'No backroom deals'
He has said he would demand they commit to reforming the tax system, more spending on education for poorer children, a switch to a greener economy and voting reform in Westminster.
He told GMTV: "There are no backroom deals between the political parties.
"If a party has got more support and has got a clearer mandate from the British people than any other party, even if they don't have an absolute majority, then I think we live in a democracy, that party has got the moral right to seek to govern, either on its own or with others.
"I've been much clearer than Gordon Brown or David Cameron in saying that as far as the Liberal Democrats are concerned, in terms of us exercising our influence, we will focus on the really big things that matter to us."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.