Nick Clegg will give his keynote address to his party's conference in Liverpool this afternoon, before jetting off to New York to attend the United Nation conference on the Millennium Development Goals.
The Lib Dem leader will use his speech to defend his decision to take the party into coalition with the Conservatives.
He is expected to tell delegates that the public would never have taken them seriously again if they had turned down power.
"People have got used to us being outsiders, against every government that’s come along," he will say.
"Maybe we got used to it ourselves. But the door to the change we want was opened, for the first time in most of our lifetimes.
"Imagine if we had turned away. How could we ever again have asked the voters to take us seriously?”
And he will seek to reassure the rank and file that their party will not be consumed by the Conservatives.
"The Liberal Democrats and the Conservatives are and always will be separate parties, with distinct histories and different futures.
"But for this Parliament we work together to fix the problems we face and put the country on a better path. This is the right government for right now."
Clegg will say that his party does not have the luxury of choosing when it wants to take power.
He will say: "Labour left the country’s coffers empty. So the years ahead will not be easy. But you do not get to choose the moment when the opportunity to shape your country comes your way. All you get to choose is what you do when it does."
Following yesterday's announcement by Danny Alexander of a £900m investment in measures to crack down on tax evasion and avoidance, the deputy prime minister will say that people who avoid paying their taxes will "no longer get away with it".
"We all read the headlines about benefit fraud," he will say. "We all agree it’s wrong when people help themselves to benefits they shouldn’t get. But when the richest people in the country dodge their tax bill that is just as bad.
"Both come down to stealing money from your neighbours. We will be tough on welfare cheats. But unlike Labour, we’ll be tough on tax cheats too."
The Lib Dem leader's speech is usually on the last day of their conference, but it was brought forward to allow Clegg to attend the poverty summit in New York.


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