The federal government met a third of the cost of its royal commission on the former government's home insulation scheme by redirecting funds from the royal commission on institutional responses to child sexual abuse.

Attorney-General George Brandis has revealed that his department's $6.7 million contribution to funding the home insulation inquiry came from savings in the child sexual abuse inquiry's capital budget and from legal assistance that was not required for witnesses to that inquiry.

"No money has been taken away from anywhere else.": George Brandis. Credit:Andrew Meares

The revelation corrects a statement by Senator Brandis to a Senate committee in February, when he was asked if there had been any offsets from other inquiries to fund the insulation royal commission and replied: ''No.''

Senator Brandis took the question on notice after saying it was his understanding that ''no money has been taken away from anywhere else''. He has since confirmed that the $19 million cost of the home insulation inquiry was equally shared by his department, the industry department and the environment department.