The federal government will struggle to constrain growth in the $44 billion National Disability Insurance Scheme at below 8 per cent, with sign-up rates expected to increase and average payment costs surging, according to Grattan Institute research.

Warning the NDIS is failing to achieve its original goals and is groaning under the weight of unsustainable work volumes, the think tank’s policy blueprint for the winner of the federal election says efforts to curb waste and fraud are unlikely to make any significant difference to the scheme’s price tag.