Liberal Democrat leader Nick Clegg has urged party doubters to "enjoy" being in power as he sought to quell internal concerns over his decision to join the Tory-led coalition Government.

The Deputy Prime Minister conceded many activists remained nervous and that the joint administration was "not always easy" but insisted it was "finally putting liberal values at the heart of British government".

He launched a staunch defence of the power-sharing deal as he opened a potentially turbulent party conference in Liverpool with a crowd-pleasing rally to launch the campaign for a 'yes' vote in next year's voting reform referendum.

Ditching the first-past-the-post system has been a key Lib Dem demand for years and securing agreement for a public vote on moving to the Alternative Vote (AV) to elect MPs was a key concession from the Tories.

But the leadership faces a series of challenges over policies where difficult compromises were struck, including education and Trident, and a slump in the party's poll ratings has fuelled concern among the membership.

Mr Clegg said that in the four months since June's election, he and fellow Lib Dem ministers had made "huge progress in delivering the changes you have campaigned for election after election, night after night, doorstep after doorstep".

He added: "I want everyone in this room to just stop and enjoy that for a second. I hope each and every one of you is as proud as I am of what we have already achieved."

He cited income tax cuts for the low paid, protecting civil liberties, criminal justice reform, ending child detention, the "pupil premium" and political reform.

"You had the courage to take the leap into the unknown, to take this party to government. Everything that has happened since has proved that you were right to do so," he went on.

"I know that being in this coalition still isn't always easy. We are a party that has always advocated pluralism - believing that politics can be better when different parties work together.

"But that doesn't mean that the nervousness some of us felt about going into government has disappeared overnight. The different impulses that, for many people here, pulled heads one way and hearts another, haven't simply vanished.

"But we've done something bold, exciting and unexpected. And, as a result, Liberal Democrats, things will never be the same for our party again."

Although the party is enjoying its first taste of power for more than 60 years, there are deep concerns among the membership over the policies it has signed up to as part of the coalition deal with the Conservatives.