Nick Clegg said the Liberal Democrats were not a party of protest, but a party of change. He told the Spring Conference that Lib Dems should "grapple" with the world and strive to make it better.
Nick Clegg has urged the Liberal Democrats to "attack" the Tories as he attempted to draw a line under damaging scandals and build on the Eastleigh by-election victory.
The Deputy Prime Minister dismissed suggestions he was abandoning the party's core values, and promised to stop David Cameron dragging the coalition to the right.
Speaking to the Liberal Democrat Spring Conference Nick Clegg the Lib Dems were no longer a "receptacle for people who don't like the world". He added:
"The Conservative party knows it needs to stay on the centre ground to have any chance of speaking to ordinary people's concerns. At least the leadership seem to. But they just can't manage it, no matter how hard they try.
"They're like a kind of broken shopping trolley. Every time you try and push them straight ahead they veer off to the right hand side..."
A spokesman for the Liberal Democrat leader Nick Clegg claims he is confident the party can take seats off Labour and "particularly" the Tories at the next general election, expected to be in 2015.
They dismissed polling by former Conservative donor Lord Ashcroft suggesting the party could lose 10 constituencies to Labour - pointing out that the peer's research predicted they would lose Eastleigh.
The spokesman also played down the idea that Business Secretary Vince Cable's call for higher capital spending funded by more borrowing was part of efforts to differentiate the Lib Dems from their coalition partners.
The Deputy Prime Minister is to insist that the risk can pay off at local elections in May and the next general election in 2015.
There is a myth that governing together, in coalition, diminishes the ability of the smaller party to beat the bigger party. The idea that, in Tory facing seats the Liberal Democrats will find it impossible to distinguish our record, our values, from theirs.
But that myth has been utterly confounded. The opposite is true. The longer you stand side-by-side with your opponents the easier your differences are to see. We don't lose our identity by governing with the Conservatives. The comparison helps the British people understand who we are.
– Nick Clegg, Deputy Prime Minister
In the days after the by-election, even though we won, I was asked how I feel about our party no longer being a magnet for the protest vote.
No longer the automatic 'none-of-the-above' choice. But the truth is: the Liberal Democrats are not a party of protest, we are a party of change. A party that is for things, not simply against things.
Deputy Prime Minister Nick Clegg will target critics in a speech today who wrote the Liberal Democrats' "political obituaries" after the party's controversies threatened to overshadow the Eastleigh by-election campaign last month.
"The odds were stacked against us. A fierce campaign, under a national spotlight, dogged by difficult headlines from day one. Extraordinary circumstances. Yet we still won," he is expected to say.
"We beat the Tories. We squeezed Labour - don't forget that bit. Why? Because, for the first time in a generation we could campaign on our record of local delivery and our record of national delivery too...
"We didn't win in Eastleigh in spite of being in power. We won in Eastleigh because we're in power - locally and nationally."
Mr Clegg will concede that some Lib Dems had harboured "quiet fears" that coalition would do irreparable damage to the party.
The Deputy Prime Minister will hail the by-election victory in Eastleigh as proof that the Lib Dems can succeed as a party of government.
He will also dismiss the "myth" that being in coalition has undermined their identity or ability to fight the Conservatives.
The rallying cry comes in a keynote speech to the Lib Dem spring conference in Brighton.
The leadership has been eager to use the gathering to move on from damaging allegations of sexual harassment by Lord Rennard - which he denies - and the conviction of former Cabinet minister Chris Huhne.