Bushfire-affected parents will get an extra $400 one-off payment for each child while volunteer firefighters will get at least $200 a day from the federal government's $2 billion bushfire recovery fund.

Prime Minister Scott Morrison hasn't put a limit on how much the government will spend on the payments, promising it will be "as much as it takes".

"I've said we will make the payments where we need to make the payments," he told reporters in Canberra on Wednesday.

Parents eligible for disaster recovery payments who have already got a $400 payment for their children will get an extra $400 to help as students go back to school. They don't need to re-apply as the new payments will flow through like the first ones.