Australia's Dyson Heydon will not step down amid claims of bias

The head of Australia's Royal Commission into union corruption has dismissed an attempt to force him to step down.

Retired High Court judge Dyson Heydon was under pressure from unions who argued that connections to the Liberal party created the perception of bias.

They argued his decision to speak at a Liberal Party fundraiser, even though he withdrew later, was problematic.

But Justice Heydon ruled that the "fair minded observer" was unlikely to agree.

"There is no reason to think that the fair-minded observer might apprehend that my intention in agreeing to give the Address was to raise funds or assist in raising funds or gathering support for the Liberal Party," he wrote in a 67-page document.

The Australian Council of Trade Unions (ACTU), aligned with Australia's Labor Party, responded by saying that the commission is "now terminally tarnished".

ACTU Secretary David Oliver called on the Prime Minister to shut down the commission and save taxpayers AU$60m ($43m; £28m).

Labor has accused Mr Abbott of using the royal commission as a political witch hunt against Opposition leader Bill Shorten.

Unions considered taking legal action to force Mr Heydon's removal on the grounds of "apprehended bias", a legal rule that judges and other officials such as royal commissioners must not only be impartial, but must be seen to be impartial.