Lawyers for WikiLeaks publisher Julian Assange have filed an appeal against his extradition to the US, as the UN human rights chief lends support to the Australian’s cause.

Assange, 51, has been indicted on 17 espionage charges in the US and one charge of computer misuse over WikiLeaks’ publication of thousands of military and diplomatic documents leaked by whistleblower Chelsea Manning.

The charges carry a maximum sentence of 175 years in prison.

WikiLeaks says Assange’s legal team filed “Perfected Grounds of Appeal” in the UK’s High Court against the US and UK Home Secretary Priti Patel, who approved his extradition in June.

Mr Assange’s lawyers argue he is “being prosecuted and punished for his political opinions”.

His wife says the prosecution is unlawful.

Years behind bars

“Overwhelming evidence has emerged proving that the US prosecution against my husband is a criminal abuse,” Stella Assange said on Twitter on Saturday.

“The High Court judges will now decide whether Julian is given the opportunity to put the case against the US before open court, and in full, at the appeal.”

Mr Assange remains in London’s Belmarsh Prison, where he has been in detention since April 2019.

A UK judge blocked his extradition last year but the US government successfully appealed in the High Court.

Prime Minister Anthony Albanese has previously stated “enough is enough” regarding Mr Assange’s ongoing detention.

The appeal comes after UN human rights chief Michelle Bachelet met with Mr Assange’s lawyers and his wife in Geneva.

Advocacy group The Assange Defense Committee told AAP they detailed to her his deteriorating health, with the Australian publisher suffering a mini-stroke recently.

-AAP