Street artist Banksy spray-paints message in red capitals on wall beside Regent's canal in north London

A new Banksy piece near the Oval bridge in Camden, north London

It may be scant compensation to disgruntled climate change activists, but the failure to agree a legally binding treaty in Copenhagen has apparently provided inspiration for the latest work by Banksy.

The street artist, whose works have sold for hundreds of thousands of pounds, has added his voice to the condemnation of the summit with one of his most rudimentary works yet. He spray-painted the words "I DON'T BELIEVE IN GLOBAL WARMING" in red capitals on a wall beside Regent's canal in Camden, north London, with the words disappearing below the water.

The new work appears to be one of four by Banksy beside the canal. The others bear more obvious resemblance to past murals by the artist, employing the stencils that are his usual modus operandi.

In one, he pictures a workman seeming to wallpaper over a patch of colourful graffiti and replace it with an expanse of grey. Another work features one of his signature rats, portrayed in a top hat and tails, while the fourth depicts a child apparently fishing out a graffiti "tag" from the canal.

Angelina Jolie and Brad Pitt are among the stars who have bought works by Banksy, who fiercely protects his anonymity but was supposedly outed by the Daily Mail last year. An exhibition of his work in his home city, Bristol, attracted more than 300,000 visitors this year. But a number of local authorities have removed his murals, and many critics have questioned their artistic value.