Campbell hits back at age critics

In a defiant closing speech to the party conference in Brighton, Sir Menzies pledged to make his "age and experience" a key issue at the next general election.

The 66-year-old insisted he would lead from the front and not be "silenced" by those who wanted to "shout him down".

He also delivered a policy surprise, calling for Britons to be given a legally-enforceable entitlement to a clean air and water - effectively extending the controversial Human Rights Act.

"We Liberal Democrats can confront the difficult issues," Sir Menzies told delegates. "Take tough decisions. Yes, and say controversial things too. That's what real leadership is about. That's what my leadership is about."

With the party desperate to end the conference on a high after a week marred by poor polls and public rowing, the pressure was on Sir Menzies as he arrived at the platform to a techno beat.

He quickly launched into an assault on the "cosy consensus" between the Government and the Tories in crucial areas such as immigration, nuclear energy and crime, insisting the Lib Dems had to "rattle the cage" of British politics.

Gordon Brown was lambasted for leading "blue Labour", and blamed for a decade eroding civil liberties, undermining the economy with unsustainable debt which had led to the Northern Rock crisis, and failing to stop Tony Blair invading Iraq.

Meanwhile, David Cameron's Conservatives were suffering from an "identity crisis" which had seen them lurch from liberal to the right, and were "not fit to govern".

Turning to speculation over his age, Sir Menzies added: "With age comes experience, and with experience comes judgment. "And when you are deciding whether to send our young men and women to war, it pays to have that experience and that judgment."