Who could get the missing $60 billion

The massively underspent JobKeeper scheme won't be expanded to workers who missed out, but it could be extended beyond six months for the battered tourism sector.

Finance Minister Mathias Cormann said the wage subsidy scheme was working as expected, despite a whopping $60 billion forecasting error.

Just 3.5 million workers have been enrolled for the $1500 fortnightly payments, rather than the 6.3 million that Treasury had estimated and budgeted for.

Arts and entertainment workers, university staff and many casual employees have been deliberately excluded from the scheme.

Senator Cormann is staring down pressure from unions and business groups who want the scheme to capture more workers.

"It is still an extremely expensive program - $70 billion is a lot of money," he told ABC radio on Monday.

Treasurer Josh Frydenberg has no plans to make wholesale changes to the scheme. But he could use the unspent money to extend JobKeeper payments beyond six months for tourism operators.

The program, which was designed to keep people connected to workplaces smashed by coronavirus restrictions, will be reviewed next month.

"The tourism sector could be one sector in need of further support," Mr Frydenberg told the ABC.

"That's what we'll look at in the context of the economic situation at the time."

Mr Frydenberg said he had taken responsibility for the forecasting mistake.

AAP