In its interim report, released on Monday, the royal commissioners sought a two-year extension, suggesting they report in December 2017. They said such an extension would allow them to conduct an extra 3000 private sessions with abuse survivors and 30 more public hearings. The extension would cost $104 million on top of its budget of $281 million.

Speaking to reporters in Canberra on Tuesday, Mr Shorten said the royal commission had been doing important work in empowering abuse survivors.

''If the royal commission said they want, or they need extra resources, if they believe they need extra time, I think that it is incumbent on the Parliament to support this,'' he said. ''Labor hopes, we fundamentally hope that the work of the royal commission can continue and that the government provides them with the resources they need so that the untold stories can be told.''

Attorney-General George Brandis has said the government is considering the request for an extension.

Since the royal commission was set up by then prime minister Julia Gillard in January 2013, it has received more than 1600 written accounts and held more than 1600 private sessions with survivors of alleged abuse in more than 1000 institutions. It has referred more than 160 matters to police.

The commission heard in private sessions that one in four abusers were members of clergy or religious orders. Of religious institutions at which abuse was reported, 68 per cent were Catholic and 12 per cent were Anglican.

Based on available data, it estimates one in three girls and one in seven boys has experienced some form of childhood sexual abuse.

The commissioners reported that if they were required to complete their work by the deadline of December next year, they would not be able to hold a private session with any abuse survivor who made contact after September this year, and could hold no more than 4000 private sessions and 40 public hearings.