Entrepreneur Dick Smith personally lobbied the United States ambassador for Washington to drop its extradition request for Julian Assange for the sake of "good relations" with Australia.

Mr Smith, who made his name and fortune with his chain of electronics stores, made his views clear in a letter to Arthur B Culvahouse Jnr earlier this year, warning the US's relationship with Australia would be "damaged" should Mr Assange be extradited from Britain.

Entrepreneur and philanthropist Dick Smith wants the United States to drop its attempt to bring Julian Assange to trial over espionage charges. Credit:James Brickwood

The campaign for the Morrison government to intervene gathered momentum on Monday after former deputy prime minister Barnaby Joyce lent his support to the WikiLeaks founder's cause.

Independent MP Andrew Wilkie also revealed that a multi-party parliamentary group to "agitate" for Mr Assange to be brought home to Australia would be launched in the coming weeks and would include some members of the Coalition government.