The Bank of England projects that the current freeze will raise £30billon by 2025-26. Think-tank the Institute for Fiscal Studies (IFS) said extending it by two years could raise a further £4-5billion.
The IFS study estimates 7.7million workers will be paying the 40p tax rate of income tax by 2025-26, compared with 4.6million if there was no freeze and thresholds rose with inflation.
Separate analysis by the Centre for Economics and Business Research suggests a further three million workers could be dragged into paying the basic and higher rate of tax during the potential two-year extension period covering 2026-27 and 2027-28.
Freezing the personal allowance and higher-rate threshold until 2026 could add a total of as much as £14,990 to the income tax bill of a worker on a £60,000 salary.
They would lose a further £8,111 if the threshold freezes were extended to 2027-28. A worker on a £30,000 salary would pay an extra £3,000 between now and 2028, of which £1,623 would be paid in the 2026-27 and 2027-28 tax years.