Museum director Penelope Curtis on the steps of Tate Britain in London. The Tate's chair, Lord Browne of Madingley, once headed BP. (Ian Gavan/Getty)

British artists are joining with environmental activists to protest BP's sponsorship of many famous U.K. galleries and museums in the wake of the Gulf of Mexico oil disaster.

Composed of musicians, filmmakers, writers and artists, Good Crude Britannia says on Monday, it will picket Tate Britain's summer party, which marks 20 years of sponsorship by the oil giant.

John Browne, also known as Lord Browne of Madingley, is chair of the Tate and was once the head of BP.

The oil company won't reveal how much it spends on the arts in Britain but it is likely to be one of the top three corporate sponsors in Britain. It is a financial supporter of the British Museum, the Tate galleries, the Royal Opera House, the National Portrait Gallery, the National Maritime Museum and the Science and Natural History Museum.

"Organizations like the National Portrait Gallery help shape public attitudes towards the big issues of the day and if the gallery is serious about climate change then the sponsorship deal with BP has got to end," Robin Oakley, Greenpeace's campaign director, told The Guardian newspaper.

On Tuesday, Greenpeace will hold an "alternative exhibition" at a private viewing at the gallery.

Monday's action — the biggest one yet by art activists — follows in the past week by another group of artists, the Greenwash Guerrillas, who distributed pamphlets outside the National Portrait Gallery at a BP-sponsored arts event.

And in May, a group called Liberate Tate entered the gallery's main hall and released dozens of black balloons attached to dead fish.

The Tate issued a statement after that incident saying that it "works with a wide range of corporate organizations and generates the majority of its funding from earned income and private sources."

It said the museum's board and ethics committee "regularly review compliance" with its sponsorship policies.