Julian Assange has found a new platform on which to press his case against extradition: the vast "little monster" fanbase of the pop star Lady Gaga, who has visited him for dinner at the Ecuadorean embassy.

Gaga dined with the WikiLeaks founder on Monday night after launching a perfume at the Harrods department store next door to the embassy where Assange, 41, has been holed up since seeking political asylum in June.

WikiLeaks seized on the apparently impromptu visit by one of the world's biggest-selling singers to urge its defenders to "educate her support base", which includes over 30 million followers on Twitter.

Assange broke his bail conditions to evade extradition to Sweden where he is wanted to face allegations of rape and sexual assault, which he strenuously denies.

He believes he faces imprisonment in the US and has claimed he could be sent to Guantánamo Bay for his role in disseminating classified US government documents.

Gaga, whose real name is Stefani Germanotta, has backed several political campaigns, notably gay rights campaigns in America. This week she urged her fans, who she calls "little monsters", to read up on fracking, the controversial technique of extracting shale gas, which campaigners complain causes environmental destruction.

Gaga's meeting with Assange was heavily plugged by WikiLeaks, which urged supporters to join protests outside the embassy and kept them up to date about Gaga's arrival. The Bad Romance singer posted pictures of the visit on her website, including one of her with Assange inside the embassy. Her trademark extravagant dress, including a witch-style hat, made for a stark contrast with Assange's plain white T-shirt.

Assange is able to accept visitors but cannot step outside the embassy because the British authorities have posted policemen at the front and back entrances who are poised to arrest him if he leaves. He would then be sent to Sweden under the terms of a European arrest warrant (EAW).

Last week, Assange's visitors included a group of financial backers who stood to lose £140,000 in bail money because of Assange's refusal to accept the supreme court's verdict upholding the EAW. On Monday a court ordered them to forfeit £93,500.

It is understood Lady Gaga was encouraged to meet Assange by MIA, the British rapper who scored the music for Assange's chatshow on Russia Today, the Kremlin-funded English language TV channel.

Gaga already has a bit part in the story of WikiLeaks. Bradley Manning, the US army private who is accused by the American authorities of stealing hundreds of thousands of classified US military and diplomatic documents, once told a computer hacker called Adrian Lamo that he "listened and lip-synched to Lady Gaga's song Telephone while exfiltrating possibly the largest data spillage in American history". He is facing trial next February, by which time he will have spent 983 days in prison without trial.