Cameron invites Lib Dems to join him in 'united front' against Gordon Brown

David Cameron has made an audacious attempt to capitalise on the change in the Liberal Democrat leadership by inviting the party to join him in a united front against Gordon Brown's authoritarian instincts.

As Lib Dem members cast their final votes in the contest between Chris Huhne and Nick Clegg, the Conservative leader made an early move to improve relations with the party, claiming they could forge a "progressive alliance" to pressurise the Prime Minister into decentralising power from Whitehall.

In an article to be published on his website today, Mr Cameron also suggested that the Green Party could be brought into an alliance which would enable them to pursue environmental objectives through the "empowerment" of individuals and communities.

The pre-emptive strike for better relations with the incoming Lib Dem leader to be announced on Tuesday threatened to isolate Mr Brown still further as his opinion-poll deficit widened.

A new poll in The Sunday Times today puts the Tories on 45 per cent, 13 points ahead of Labour on 32 per cent. The YouGov poll showed the Lib Dems, led by caretaker leader Vince Cable, on 14 per cent.

Mr Brown's personal approval rating has also slumped to minus 26 percentage points, down from minus 10 percentage points last month, amid the fall-out from Labour's "proxy donor" scandal, the loss of HM Revenue & Customs' child benefit database, and threats of a police strike.

Mr Cameron's overtures will be seen as an attempt to profit from the instability in the party and the Government's problems, as much as a genuine attempt to force improvements in British democracy.

"Political parties, even though they may have serious disagreements over aspects of policy, should work together in areas where they agree," he said in the article.