Lloyds Banking Group and Royal Bank of Scotland, Britain’s part-nationalised banks, will outline moves to raise a combined £54bn in fresh funding on Tuesday, in a startling reshaping of Britain’s finance industry.

Alistair Darling, chancellor, will confirm that the government will contribute more than £30bn of the new capital. He will also announce an emergency £8bn “contingent equity” fund to rescue RBS in the event of a future financial crisis.