The IBAHRI works with the global legal community to promote and protect human rights and the independence of the legal profession worldwide.

Mr Assange’s extradition trial began last month and will resume in May. The controversial activist is wanted in the US on 18 charges of attempted hacking and espionage.

He is alleged to have collaborated with former US army intelligence analyst Chelsea Manning to leak classified documents which he said exposed alleged war crimes in Afghanistan and Iraq.

Mr Assange’s lawyers claim he has been handcuffed 11 times; been stripped naked twice and searched; had his case files confiscated after the first day of the hearing; and had his request to sit with his lawyers during the trial, rather than in a dock surrounded by bulletproof glass, denied.

Michael Kirby AC CMG, co-chair of the IBAHRI, said the alleged treatment amounted to “gross and disproportionate conduct”, especially where Mr Assange has not been accused of “personal violence”.

The former Australian judge added: “It is deeply shocking that as a mature democracy in which the rule of law and the rights of individuals are preserved, the UK Government has been silent and has taken no action to terminate such gross and disproportionate conduct by Crown officials.

“As well, we are surprised that the presiding judge has reportedly said and done nothing to rebuke the officials and their superiors for such conduct in the case of an accused whose offence is not one of personal violence.

“Many countries in the world look to Britain as an example in such matters. On this occasion, the example is shocking and excessive. It is reminiscent of the Abu Grahib Prison Scandal which can happen when prison officials are not trained in the basic human rights of detainees and the Nelson Mandela Rules.”