The interim report from the royal commission investigating child abuse in institutions will be delivered to the government on Monday.

The report is expected to reveal that the scale of child sexual abuse in Australian institutions is far wider than expected and the potential for it to happen still exists.

It will also outline the need for an extension on the date which has been set for its final report, December 31, 2015.

The report should be made public within days once it has been considered by the federal department of the attorney-general.

It has been delivered to the Governor-General Peter Cosgrove.