An increased windfall tax should be imposed on the UK’s largest banks according to trade union leaders, after the big four lenders reported almost £14bn in first-quarter profits, partly fuelled by market turbulence caused by the Iran war.

The Trades Union Congress (TUC) renewed its call for an increase in the current bank surcharge, which was reduced from 8% to 3% of profits above £100m by the Conservative government in 2023, as banks benefit from the high interest rate environment.

The Bank of England held interest rates at 3.75% last week , with markets pricing in up to two increases by the end of this year.…