The question is vexing many, not least the UK Treasury, which stands to lose revenue, and face, if there is a widespread emigration.

A recent meeting held by KPMG in Berlin gave some indication.

The firm polled 120 multinational companies and found that 62% were planning to move assets or operations to low tax regimes.

The headline figure, however, fails to reveal quite what is going on in the area of moving HQs.

The firm held a breakout session on the issue of moving HQs at the conference, attended in large part by UK-based multinationals.

'It was one of the best attended sessions of the conference,' said Anneli Collins, head of international corporate tax at KPMG.

There are, however, a number of complexities. For example, companies would be likely to trigger a capital gains charge in moving, but that might not impact on most.

The real problem was the controlled foreign companies (CFC) legislation, Collins said.

CFC rules would mean that the company would be taxed in the UK as if it were headquartered here, unless a further company were put in place above it. But that would require a relisting, in London or elsewhere, presenting a real barrier to most pondering the issue.

It might also mean, subject to negotiation, not being included in the FTSE 100 list, one of the key requirements of which is UK nationality. Would companies be prepared to forfeit that?

Collins said it was a live issue: 'Companies are not rushing for the boats, but the issue is bubbling away under the surface.'