Standard Life would back HSBC if the bank decided to abandon the City and move its headquarters to Asia or the US.

David Cumming, head of equities at Standard Life Investments, which holds a 1.5per cent stake in the UK’s biggest bank, said banks had been put under relentless regulatory pressures and there was a risk they would lose patience.

Mr Cumming said in a radio interview that stress-tests were needed to ensure banks had prudent amounts of capital, but went on: “I think this ongoing process of continually...this, sort of, almost there in terms of getting to capital targets, moving the goalposts and the Financial Policy Committee coming up with new wheezes in terms of getting the banks to hold more capital - I think the banks are losing patience and I think HSBC, who could move, are very, very close to losing patience with this never ending process and, to be honest, I think a lot of shareholders, including ourselves, if they did move we would be supportive of that, given the current situation in terms of regulation.”

Asked to confirm SLI would back such a decision, Mr Cumming said: “Well, given the situation where there is no clear end point in terms of ever increasing capital requirements, and the fact they're getting put out of competitive advantage, and the fact that we will see better growth in earnings and dividend prospects should they move, unless the regulator changes tack then logically we would be supportive of a move, if they choose to do that.”

The warning came as the Bank of England prepared its latest set of stress tests, designed to assess whether lenders could withstand another financial crisis.

HSBC has been domiciled in the UK since the early 1990s after it bought Midland Bank and moved its headquarters from Hong Kong.

Last April a fortnight before the general election, the bank’s chairman, Glaswegian Douglas Flint, launched a review under chief executive Stuart Gulliver of its domicile. In a warning shot to a new government, he cited factors such as the UK's tax regime and uncertainty over the country's membership of the EU, as well as the rapid growth of emerging market economies. Mr Flint said the review, which was reported to have been well received by major shareholders, would be completed by the end of this year.

The chancellor appeared to respond in his July budget, by announcing that the bank levy would be gradually reduced over the next five years and replaced by a tax on profits – which smaller lenders have complained will hit them hardest.

It had been assumed that Hong Kong was the obvious candidate for any move, but last month the US emerged as a serious alternative, because of growing concerns about political risk – that the bank could end up under Chinese control.

Advisers to HSBC believe the US has an economy big enough to accommodate such a large bank, and that US regulation is less intrusive. They are also concerned that a move to Hong Kong would upset UK and US regulators, with potentially negative consequences for the bank.

It was also reported that bank executives still felt the attitude of the UK Treasury and regulators was “hostile” towards big banks.

A month ago Mr Flint said the bank was only “halfway through” the process and it would update shareholders at its next results in February.