The new leader of the Liberal Democrats, Sir Menzies Campbell, has told their Scottish spring conference that the party "is back in business".
Sir Menzies said the party must seek power
Addressing delegates in Aviemore, he said recent Scottish by-election success had proved commentators wrong about the mood of Britain.
And he said Lib Dems should move from a party of protest to a party of power.
Responding to press reports about atomic issues, Sir Menzies said he was opposed to new nuclear power stations.
Views on energy issues are likely to divide the Liberal Democrats from Labour when it comes to next year's Holyrood elections.
Sir Menzies went on to criticise the prime minister for turning Westminster into a "graveyard of democracy", and he accused Tony Blair of reducing civil liberties and waging an illegal war in Iraq.
He also accused the Conservative leader, David Cameron, of trying to steal the Liberals' clothes.
Sir Menzies said it was time for devolution to be taken a step further and called for a written constitution for the whole of the UK.
He insisted his party's recent triumph in the Dunfermline and West Fife by-election showed Liberal Democrats could mount a challenge in any part of the UK.
"We are the driving force in Scotland," he said, "but we can also be the driving force across the UK."
He called on delegates to "take the spirit of Dunfermline to every corner of the country".
In February, Willie Rennie achieved a shock result by overturning a huge Labour majority in the neighbouring constituency to that of Chancellor Gordon Brown.