Treasury select committee asks FCA to investigate whether tax surcharge leak led to ‘improper release of inside information’

John Healey is facing pressure to clarify whether he permitted a market-sensitive budget leak ahead of his statement, which moved bank share prices.

The chair of the influential Commons Treasury select committe, Meg Hillier, has written to the Treasury and the Financial Conduct Authority watchdog (FCA) to assess whether a story leaked to Bloomberg, and published more than an hour before the budget was revealed, led to an “improper release of inside information”.

Chancellor’s predecessor Rachel Reeves had planned to reduce allowance from £20,000 to £12,000 a year from April

• Business live – latest updates

• What to expect from the budget: who wins, who pays?

John Healey is to use his first budget to ditch plans to slash the annual cash Isa allowance, the Guardian understands, preferring a carrot rather than a stick to encourage people to invest more in shares.

City experts welcomed news that the chancellor will overturn a decision by his predecessor, Rachel Reeves, to cut the allowance from £20,000 to £12,000 a year from April to get more money flowing into UK company stocks.