The Guardian reported that a senior official at HSBC, whose operations span over 70 countries, had said Britain may no longer be an attractive place to be based for tax purposes.

"It is not true that we might be leaving Britain for tax reasons," an HSBC spokesman said, adding the bank's next review of the location of its headquarters and other major offices was not due for about 18 months.

"One of the benefits of London in the past has been a relatively good tax regime. The UK needs to be aware of that being one of its competitive advantages," he said, adding the regulatory environment was also an important factor.

"It would be possible to go somewhere where there is zero corporation tax which would save us in the region of 400 million pounds a year. But those places tend not to have regulators as complex and aware as the FSA (Financial Services Authority).

"As much as banks moan about regulation from time to time, having your HQ based with a good and globally renowned regulator builds customer credibility. If we were to lose that then we would have a problem," the spokesman said.