The federal government is expected to ditch one of its most controversial budget measures - the plan to apply real interest rates to student debts - following advice from the architect of the HECS repayment scheme that it is unfair to poor graduates.

Modelling by education economist Bruce Chapman has found poor graduates could pay 30 per cent more for a degree than their high-income counterparts if the government indexes student debts at the government bond rate rather than inflation. Women who take time off work to have children would be among the hardest hit.

Education minister Christopher Pyne has received advice from leading education economist Bruce Chapman that the HECS budget measures are unfair to poor graduates. Credit:Alex Ellinghausen

Professor Chapman's paper, which has been presented to Education Minister Christopher Pyne, presents two alternative interest-rate proposals that would reduce inequity concerns but have only a small impact on the budget.