Clive Palmer has backed allegations Peter Slipper has made in Parliament that Liberals Joe Hockey and Mal Brough requested the billionaire pay the legal fees of Mr Slipper's former aide James Ashby.

Joe Hockey has denied the allegations, and demanded Mr Slipper, a former Liberal party member, withdraw the suggestion the shadow treasurer was linked to the Ashby affair.

The controversy began when Mr Slipper rose in Parliament on Thursday to give what he called his “precautionary valedictory speech” in case he loses in the upcoming federal election and does not return to Parliament.

Between thanking family and friends, Mr Slipper recalled a breakfast he had recently with Mr Palmer at the billionaire's resort in Queensland.