In his first speech as Liberal Democrat leader Sir Menzies Campbell has said he wants to create a fairer society.
He earlier told the BBC he would consider a 50% top tax rate - a policy being reviewed after the 2005 election.
In his speech he said there had been "too much attention" on this policy but he would cut taxes for the poor without increasing the overall burden.
He also pledged fresh ideas, saying he wanted the party to be a "rallying point for a new Liberal Britain".
Sir Menzies attacked the "managerial" politics of the Conservatives and Labour saying: "We've had enough of Blairism.
"The country is crying out for a principled liberal democratic alternative."
He attacked the "outrage" of Guantanamo Bay, mocking Mr Blair's description of it as an "anomaly".
"Once Westminster was the cradle of democracy; Under this government it is becoming the graveyard of democracy," Sir Menzies told delegates.
He said people who expected him to "tread water" as leader were in for a "rude shock".
He pledged to shake up his party's communication strategy and bring in more women and ethnic minority candidates.
Over the next six months he will set out "key challenges and policy directions", he told delegates, on areas including the economy, the environment, welfare reform, better government, education and skills, crime and social policy.
He pointed to the recent Dunfermline by-election as an example of how the party can put recent difficulties behind it and still challenge both Labour and the Tories.
On tax he warned against becoming "fixated" with the 50% top rate, saying the tax system should be based on three principles: less tax for the poor, help for the environment and to be "simple" to "support enterprise not stifle it".
Summing up his vision for the party, he said: "Let us pledge today that where we see unfairness we will challenge it; Where we see injustice we will attack it; And where we see prejudice we will confront it."
Speaking earlier to the BBC's Andrew Marr, Sir Menzies hit back at speculation he would lead the party to the right, saying he was a politician of the "centre left".
On the 50% top rate of tax proposal, he said: "I found it quite easy to defend that in the last election campaign and I would find it easy to do so again."
He said he was "firmly opposed" to nuclear power and said aviation fuel should be taxed as it was "making enormous impact on climate change".
Asked about Tony Blair's belief that he will be judged by God over the Iraq war, he said: "I have never doubted the prime minister has strong faith."
But he said other considerations - such as the consequences and "unintended consequences" of invasion - should have been taken into account.
He said the Iraq war had been an "illegal" conflict which had done "very substantial damage to Britain's reputation in the world and in particular in the Middle East".
But he stressed his "internationalist" credentials, revealing he had once considered applying for American citizenship.
"It was a long time ago when I was a student," he added.
Sir Menzies' first indication of how he sees the Lib Dems progressing will come when he unveils his shadow cabinet next week.
It is expected he will announce who will get the Treasury, home and foreign portfolios on Monday, with the remainder of the jobs being announced a couple of days later.