The ratio of tax to GDP has breached the 23.9 per cent benchmark after a bigger-than-expected budget surplus from surging income tax receipts and resources companies’ profits, and risks becoming permanently entrenched, economists warn.

As Prime Minister Anthony Albanese and Treasurer Jim Chalmers face pressure to spend a surplus now nudging $20 billion, business groups also warn splurging the windfall could fuel inflation and further interest rate rises.