Commission just 'business as usual': PM

It's "business as usual" at the royal commission into trade union corruption, after Dyson Heydon decided he's staying, Prime Minister Tony Abbott says.

A day after the commissioner chose to remain at the helm, despite a union push to have him disqualified over perceived bias, a hearing is underway in Sydney involving ACT CFMEU officials.

"Today it's business as usual, various union officials are being called.

"Rorts, rackets and rip-offs inside the union movement are being exposed," Mr Abbott told reporters in Canberra.