Film star Bill Nighy was among actors urging vote-hungry politicians to support the Robin Hood Tax as an artwork has been unveiled telling candidates the decision was a "no brainer".

Nighy, who played ageing pop star Billy Mack in Love Actually, was joined by Harry Potter star Tom Felton, Doctor Who's Noel Clarke and Joe Dempsie from Skins to urge politicians to consider the tax on banks' financial transactions.

The No Brainer artwork, created by anonymous street artist Dr D, shows Gordon Brown and David Cameron with the top of their heads chopped off and Mr Cameron holding a tiny brain. It bears the message "Support the Robin Hood Tax - It's a no brainer."

Nighy said the tax was "a beautiful, simple thing, easily achievable" and the Robin Hood Tax campaign already had the support of hundreds of thousands of people.

"We urge our political leaders to listen to them and endorse the introduction of the tax," he said."The Robin Hood Tax is a tiny levy that could make the difference to many people in the UK and abroad, that will cost us personally nothing."

Despite the political content of the "witty" artwork, Nighy said the wider campaign was not about politics but was about making a difference to societies home and abroad.

In the UK that could mean more money to tackle child poverty, provide affordable housing and get people out of the benefits trap, he said.

The unveiling of the artwork, which has been pasted on to the front of Cordy House in Shoreditch, east London, coincided with the historic first televised debate between the leaders of the three main parties.

Nighy said: "I hope that they will talk about it. I hope it's acted upon."

Mutate Britain, an east London-based arts movement which unveiled No Brainer, is holding a free public art exhibition at Cordy House on Saturday and Sunday from 11am to 8pm.