My age and experience are a virtue, says defiant Campbell

Sir Menzies Campbell faced down his critics with a fighting conference speech, declaring he had the "energy, ambition and determination" to lead the Liberal Democrats to success in the next general election.

He won a five-minute standing ovation from activists after he pledged to speak up for the "voiceless and marginalised", promised to put the environment at the heart of the party's appeal to voters and warned those sceptical of his leadership: "I will not be silenced".

Sir Menzies, 66, shrug-ged off a conference week dogged by damaging headlines about his age and style, constant speculation over who might replace him and poor opinion poll ratings. He won applause as he told delegates to be ready for a snap election, adding: "I believe there is some speculation that age will be a factor.

"You bet it will, because I'm going to make it one – because with age comes experience and with experience comes judgement." The Liberal Democrat leader used his 45-minute address in Brighton to outline far-reaching plans for a new green "bill of rights" and vowed to defend the "five freedoms" of opportunity, health, security, prosperity and the environment.

He mounted his stron-gest attack yet on Gordon Brown in a clear bid to woo disaffected left-leaning Labour supportersand rebut charges that he was too close to the new Prime Minister. Sir Menzies said: "In spite of your claims of change, Mr Brown, not much really has changed. New Labour remains blue Labour." He added: "You're still wrong: wrong on nuclear energy, wrong on council tax, wrong on student fees. And you are wrong, wrong, wrong on detention without charge.

"We don't just need a change of tone in this country – we need a change of policies. And you, Gordon Brown, have not delivered."

Sir Menzies condemned David Cameron as a man "without convictions of his own... buffeted by the beliefs of others." And he accused the Tory leader of inflaming the Northern Rock crisis "with rash words", insisting that the Conservatives were not fit to govern.

The Liberal Democrat leader said the two largest parties had created a "cosy consensus" on a string of issues from nuclear power and tuition fees to the Iraq war and green taxation. He declared: "I don't want to be like any of them."

Sir Menzies hit back at critics who say the party is being squeezed out of its unique place in British politics as Labour and the Tories converge on the centre ground. He said his party presented the only real alternative to voters disillusioned with Mr Cameron and Mr Brown. He added: "Only we can achieve a free, fair and green society, because only we believe in it. Only we will work for it, only we will fight for it."

Departing from his text, Sir Menzies joked about his wife Elspeth's encounter with Nick Clegg, the party's home affairs spokesman, who reignited leadership speculation earlier in the week. He said: "I was a young Turk once and if you saw the television news last night you can see I married one." Squaring up to doubters who have attacked his leadership style, he won cheers as he insisted: "You might have noticed this week that we have one or two critics in the media. Well I'm happy to say that I answer to you and not to the media."

He went on: "We Liberal Democrats can confront the difficult issues, take tough decisions and, yes, say controversial things too.

"That's what real leadership is about and that is what my leadership is about. That is why we the Liberal Democrats are the cutting edge of the debates on tax, poverty and crime, and I won't have it any other way.

"When we go into the next election I will tell the hard, uncompromising truths about the state of this country and about the radical action needed to change it. That's the honest way to earn people's trust, that's the only way to earn people's trust."

Sir Menzies spoke of private meetings he had held in recent months with the "marginalised and rejected", including a young musician who could not afford to go to university, a woman drug addict in prison and a soldier recovering from terrible wounds suffered in Iraq. He said: "There are too many forgotten people in Brown's Britain, people who don't make the headlines. Things have to change if we want our country to be one truly united Britain."

Sir Menzies outlined plans for a bill of rights guaranteeing every citizen the right to clean water, pure air and unpolluted land giving, them the power to go to court to challenge developments that might threaten the environment.

The main points

* The Liberal Democrats are ready for the next election and are determined to "rattle the cage" of British politics when it comes.

* Sir Menzies' age will be a bonus at the election because "with age comes experience".

* Labour and the Tories have built a "cosy consensus" – and the Liberal Democrats offer the only real alternative.

* The environment has been degraded and civil liberties eroded under Labour.

* The Lib Dems must speak up for the voiceless and marginalised and speak out against "intolerance and extremism".

* A bill of rights should be introduced, putting the environment at the heart of the constitution.

* It falls to the party to make the "overwhelming case for the EU".

Buzzwords

No of times mentioned

Liberal: 32

Britain: 12

Environment: 11

Brown: 11

Cameron: 4

Cosy: 3

Age: 2