The revelation Julian Assange's confidential conversations with his Australian lawyers were secretly recorded should force the British courts to throw out attempts to extradite him to the United States, independent MP Andrew Wilkie says.

Mr Wilkie has again called on Prime Minister Scott Morrison to lobby the British government to reject the United States attempts to extradite Australian-born WikiLeaks founder who faces several espionage charges over the publication of hundreds of thousands of confidential government documents.

A Spanish private security company is under investigation over allegations it spied on Mr Assange while he was living at the Ecuadorian embassy, passing on hundreds of hours of recordings and other surveillance to American intelligence, according to former workers at the Spanish company.

The ABC reported on Sunday that Mr Assange's Australian lawyers, including prominent QC Geoffrey Robertson, were also among those spied on in "Operation Hotel".