Former treasurer Peter Costello has slammed the Turnbull government's budget strategy, predicting he will die before the nation's finances return to a healthy state and calling for spending to be slashed by at least $18 billion a year to fix the problem.

In a pointed attack on the eve of Treasurer Scott Morrison's third budget, Australia's longest serving treasurer said the Coalition had not done enough to control debt and forecast it would take at least 10 years of surplus budgets before it is paid off.

Former treasurer Peter Costello says spending needs to be cut to help pay down debt. Credit:Josh Robenstone

"We've now had 10 years of deficit, cumulatively that means to cover that we have had to borrow about $370 billion. We went from having no net debt to borrowing about $370 billion. That money doesn't go away. It's going to be there, we're going to be paying interest on it, until somebody pays it back," he told ABC's 7.30 program on Monday night.

Asked about the impact of the government's fiscal strategy, Mr Costello said it means that future generations will be paying interest on the debt that is being run up on their behalf over the last decade, and they will probably be paying for the rest of their lives.