Commission just 'business as usual': PM

A day after Dyson Heydon chose to stay on as royal commissioner, Prime Minister Tony Abbott says it's business as usual for the inquiry into trade unions.

Prime Minister Tony Abbott says it's business as usual for the royal commission into trade unions. (AAP)

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.