New accountants, architects, social workers and vets would be among those forced to pay back their HECS loans from their first days in the workforce under a controversial proposal to slash debt repayment thresholds.

The hit would come as many recent graduates already struggle to afford record rents and save for a house deposit, with wage growth at its lowest point since the early 1990s.

The influential Grattan Institute think tank has proposed reducing the initial repayment threshold for student debts from an annual income of $54,126 to $42,000. The move, designed to recoup more debt from female and part-time graduates, would save $500 million a year when accompanied by other changes, and aim to offset the ballooning $3 billion debt from the scandal-ridden private college sector.

On Tuesday, Treasurer Scott Morrison confirmed the government was examining changing repayment thresholds for the Higher Education Loan Program - which covers university and vocational graduates - as part of its budget deliberations.