The chancellor has been urged to cut taxes, after new data showed borrowing costs had fallen.
But the government is still in danger of missing its fiscal targets, despite rising tax receipts and a lower than expected debt interest bill.
Martin Beck, economic adviser to the EY Item Club, said the Office for Budget Responsibility was likely to warn that the chancellor will not meet his target to have debt on a declining path in the next five years or to balance day-to-day spending.