Costings release is up to Shorten: PBO

The Parliamentary Budget Officer says he can't release the detailed costings of Bill Shorten's budget-in-reply promises.

Mr Shorten set out an alternative plan to fund the national disability insurance scheme in his speech to parliament on Thursday night.

Rather than lift the Medicare levy to 2.5 per cent for all workers, Labor wants to limit it to those earning more than $87,000 a year.

Finance Minister Mathias Cormann said Mr Shorten should release the PBO costings relied on to make his "fudged figures" claim about matching the government's budget plan.

Phil Bowen, who heads the PBO, told AAP on Friday he was unable to release costings his office had prepared on a confidential basis.

"For confidentiality reasons I cannot add to what Bill Shorten said in his speech last night in relation to costings prepared by the PBO," he said.