The UK government on Tuesday doubled its bet on bailing out Britain’s two part-nationalised banks – Royal Bank of Scotland and Lloyds Banking Group – adding up to £37bn of new money to the same sum it first injected a year ago.

The latest chapter in the bail-out saga makes RBS by far the world’s biggest government rescue, taking as much as £53.5bn of state money, compared with the $45bn (£27.4bn) absorbed by Citigroup in the US.