Labour has unveiled its secret weapon in the battle against David Cameron's resurgent Conservative Party, a little blue lizard that changes colour to match his political environment.

'Dave the Chameleon' is the star of Labour's party political broadcast for the May 4 local council elections, which is being televised tonight. The broadcast claims that the Tory leader flip-flops between being red, yellow and green - but his real core is blue.

To the soundtrack of the 1983 Culture Club hit Karma Chameleon, the film briefly recounts the life of the Dave, the blue chameleon, who joins a bunch of blue friends in a "little blue party called the Conservatives" then, during a brief career in PR, learns "how to change into any colour he pleased".

He soon works out that telling people what the Conservatives really stood for would never make them popular, so he decides only to tell people whatever he thought they wanted to hear, "whether he in the blue party liked it or not".

The broadcast lampoons Mr Cameron for telling red Labour supporters he was the "heir to Blair", and the yellow Lib Dems he was "a liberal Conservative". It also mocks his bicycle-riding green credentials.

"Dave the chameleon changed into every colour of the rainbow as he told everyone just what he thought they wanted to hear," it says. "But underneath it all he was still true blue, through and through."

The film has been produced for the local elections, but Labour revealed that it will stick with the character after polling day, following up with mobile phone ringtones, podcasts and other internet downloads.

The Cameron-chameleon gibe was first used by John Prescott, the Deputy Prime Minister, at the Labour conference.

"This image shows exactly what David Cameron represents - a political chameleon who says whatever he thinks his audience wants to hear," Mr Prescott said of the new cartoon character.

"We keep seeing different versions of him - Liberal Cameron, new Labour Cameron, Green Cameron. He may change his colour at will, flip-flopping from one position to another, but underneath he is Conservative to the core."

But Mr Cameron - who today launched the final phase of the Tory local election campaign under the slogan "Vote Blue, Go Green" - dismissed the attack and contrasted the film with an "entirely positive" Tory broadcast about what the party’s councils were doing.

"Labour are clearly showing that they have run out of steam, run out of ideas, run out of positive things to contribute either at the local level or the national level and this would seem to be the evidence," he said.

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