Lawyers for Julian Assange have opposed an attempt by the US to overturn the block to his extradition, arguing that assurances over its potential treatment of him are “meaningless” and “vague”.

Assange, 50, is wanted in America on allegations of a conspiracy to obtain and disclose national defence information following WikiLeaks’s publication of hundreds of thousands of leaked documents relating to the Afghanistan and Iraq wars.

Then-District Judge Vanessa Baraitser ruled in January, following a multi-week hearing, that Assange should not be sent to the US, citing a real and “oppressive” risk of suicide.