BRITAIN'S "big five" high street banks could be forced to sell branches to smaller competitors under Labour plans to impose a cap on their market share.

Ed Miliband is expected to say in a keynote speech tomorrow that a Labour government would order regulators to look at whether there was sufficient competition in the retail banking sector. He is also due to say customers should have a permanent account number to make it easier to switch banks.

Chris Leslie, the Shadow Chief Secretary to the Treasury, said the party leader would set out plans to inject "competition and hunger" into the sector. "This is about change and reform. The Government have fallen short consistently of rising to the challenge."

A Conservative Party spokesman said: "Labour's failure to regulate the banks, the financial crisis and the worst recession in a century have left hard-working people with less choice over who to bank with. Once again, Ed Miliband is talking about a problem created by his Labour government."