Dressed in black and carrying black umbrellas, the protesters sang and performed a dramatisation of an oil spill, before sitting down on the floor in the museum's great court in lines forming the word "No".

The demonstrators carried banners reading "end oil" and "no new BP deal".

Protester Yasmin de Silva, who protested at Tate Britain before joining a larger protest at the museum, called BP "one of the dirtiest and most controversial oil companies in the world" and called their cultural sponsorship "incongruous".

"Unfortunately, oil companies like BP are doing all they can to prevent meaningful action on climate change from taking place," de Silva said.

"Tate, the British Museum and other London cultural institutions are explicitly endorsing them in doing it."

The British Museum, which offers free entry and is visited by almost seven million visitors a year, describes BP as its "most longstanding corporate partner".

Most recently, the energy company has sponsored two major exhibitions "Indigenous Australia: enduring civilisation" and "China: Journey to the East".

BP did not immediately respond to a request for comment. afp