Being 66 makes me a better leader, angry Ming tells his critics

He challenged accusations that his stewardship is stuttering with a call for party unity.

And he stressed that the Lib-Dems are the only alternative to the 'cosy consensus' growing between Labour and the Tories.

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After a turbulent week marked by bitter infighting between potential successors, Sir Menzies virtually eliminated any possibility of a coup before the next general election.

In a combative and sometimes angry address, he hit back at critics who say that at 66 he is too old to take on David Cameron, 40, and 56-year-old Gordon Brown.

Delivering a sideswipe to the "young Turks" jockeying for position to succeed him, Sir Menzies even vowed to make age an issue at the next election, declaring that "with age comes experience, and with experience comes judgment".

He vowed to lead with "energy, ambition and determination".

In his 45-minute speech he also promised to "rattle the cage" of British politics and continue taking "tough, controversial decisions" in the country's best interests.

Sir Menzies sought to distance himself from the "comfortable, cosy and complacent" consensus between Labour and the Tories.

He said there is little difference in their policies on issues including the "illegal and disastrous" war in Iraq, the NHS, climate change and immigration.

Sir Menzies blasted Mr Brown for being complicit in the "waste, failure and disappointment" of Labour's decade in power.

Mocking New Labour as "blue Labour", he said the Prime Minister must be held to account for eroding civil liberties, undermining the economy, failing to stop Tony Blair invading Iraq, raiding private pensions and overseeing a huge rise in home repossessions and personal debt.

Sir Menzies said: "We don't need a change of tone in this country, we need a change of policies.

"There are too many forgotten people in Brown's Britain."

Turning his fire on Mr Cameron, he said the Tories are suffering an "identity crisis" which had seen them lurch to the Right. They were not fit to govern.

Sir Menzies jibed: "Last year, the Conservative conference was about health, happiness and the sunshine glinting through the trees.

"This year, it will be flag, fear - and foreigners."

He told delegates: "Our mission is to change the political landscape, once and for all.

"When people ask me what I feel about the state of Britain today, I say I'm angry.

"Deeply angry. Things have to change if we want our country to be one truly united Britain.

"Whether you are black or white, male or female, rich or poor, gay or straight, sick or healthy, young or old.

"Government must stand for the interests of all, but the vested interests of none."

Sir Menzies said he would fight for "five freedoms" for people - opportunity, good health, personal security, prosperity and a clean environment.

The LibDems would cut the basic rate of income tax to 16p, introduce a raft of "green" levies to curb pollution, put more police officers on the beat and invest in disadvantaged pupils.

His speech was peppered with jokes and produced more than 35 rounds of applause.

At the end, delegates gave their leader a five-minute standing ovation and enthusiastic cheers as he stood with his wife Elspeth on the podium.

It marked a triumphant end to a conference which had looked as though it would be dominated by a slanging match between home affairs spokesman Nick Clegg and environment spokesman Chris Huhne, the rising stars expected to fight to succeed the leader.

Mr Clegg described Sir Menzies's speech as "excellent", Mr Huhne said it was "outstanding" and former LibDem leader Lord Ashdown said it was a "classic" that would have sent activists home with "a song in their heart".