Supporters of Julian Assange will hold a picnic opposite Parliament on Saturday to mark the 50th birthday of the WikiLeaks founder.

There will be giant picnic blankets in Parliament Square stencilled with a Free Assange slogan, and the Australian’s partner Stella Moris will cut a birthday cake.

It will be the third birthday he has spent in the high-security Belmarsh prison in London.

His supporters sailed past Parliament and the US Embassy earlier this week as part of a growing campaign to free him.

An attempt to extradite Assange to the United States was rejected in January, but he continues to be held in prison pending an appeal.

Ms Moris told the PA news agency that the US case had “sunk”, adding there is growing support across the world for Assange to be released.

Julian Assange
The event will mark Julian Assange’s 50th birthday on Saturday (PA)

She said: “The longer this goes on the clearer it is that this is a political case. Julian should be at home with me and our two children.

“This has gone on far too long – it has to stop. He is not a criminal.”

Ms Moris has asked the authorities in Belmarsh if the couple can get married, saying it should be a right for anyone.

She hopes Assange will be granted permission to get married outside the prison.

“We will celebrate his birthday – and have cake,” she added.

A number of Australian politicians have appealed to the US Government to drop its Espionage Act charges against Assange.

The MPs and Senators urged US President Joe Biden to take the “opportunity for urgent reconsideration”, following a UK court’s decision to deny the US extradition request earlier this year.

John Rees, who organises events to keep up the pressure for Assange’s release, said: “Momentum is building across the world for our campaign. The case against Julian is collapsing.”