Julian Assange's father has engaged a silk to start legal action against Australian Prime Minister Tony Abbott and Foreign Minister Julie Bishop over comments relating to his political party's controversial visit to Syria.

John Shipton came under fire after the Australian WikiLeaks Party sent a delegation to Syria to meet accused war criminal, President Bashar al-Assad.

Julian Assange's father, John Shipton. Credit:Justin McManus

Mr Shipton is claiming that the comments made by Mr Abbott and Ms Bishop defamed him.

"Because of the defamatory statements made against myself by Prime Minister Tony Abbott and Foreign Minister Julie Bishop, we have asked barrister Clive A. Evatt to begin defamation proceedings seeking $5 million in damages in each case," he said.