The surprise departure of two of Britain’s top bank executives has raised the stakes in the heated debate over the industry’s future in London, with new leaders at Barclays and HSBC set to face off with the government over bank reforms.

The abrupt resignation of Stephen Green, HSBC’s executive chairman, for a role in government and Barclays’ unexpectedly swift promotion of Bob Diamond, one of the world’s best-paid investment bankers, to replace John Varley as chief executive has intensified speculation about the groups’ commitment to the UK amid an inquiry into whether big banks should be broken up.

Both banks have warned that forcing them to hive off their highly profitable investment and corporate banking operations from their less volatile retail businesses could see them shift their headquarters abroad.