Business leaders sought urgent clarification from Alistair Darling last night on the rules around corporate tax after Regus, the office rental group, became the third company in as many days to say that it was quitting Britain for more a favourable tax regime.

The company said that it planned to move its headquarters to Luxembourg and would create a UK holding company in Jersey called New Regus.

Explaining the decision to leave, Regus said that the change would “help protect Regus Group’s taxation position given the ongoing uncertainty surrounding the UK tax treatment of international groups whose holding company is UK tax-resident”.

Regus’s decision follows those of Henderson Group, the asset manager, and Charter, the engineering company, both of which announced this week their intention to relocate to the Republic of Ireland for tax reasons.

John Cridland, deputy director-general of the CBI, said that the departures underscored the need for the Chancellor to clarify his tax policy for multinational companies with headquarters in the UK that generate significant profits offshore.

“He has to do more. He needs to be bolder and he needs to be clearer,” Mr Cridland told The Times. “People don’t know what to expect and that is not a good position to be in.”

The Treasury triggered controversy last June when it proposed changes to the taxation of companies’ foreign profits. That prompted at least two companies — United Business Media and Shire Pharmaceuticals — to say that they would move their headquarters offshore, while several others, including WPP, the media giant, threatened to follow suit.

Last month, after a series of meetings with business leaders, Mr Darling backtracked on the bulk of the proposed changes, although he kept the door open for further refinement of the rules down the line.

Mr Cridland said it was precisely that uncertainty that was driving businesses away: “The problem is that the Government has done such damage to business confidence in its commitment to tax competitiveness that it needs to do a lot to recoup the lost ground.”

Chris Sanger, tax partner at Ernst & Young, said that there was “a whole series of companies” that were looking to move offshore and that Mr Darling needed to act “as soon as possible” to stem the tide. “There is an urgent need for a clear statement of principal by the Treasury that the UK only wants to tax profits made in the UK and those diverted from the UK,” he said.

The Treasury emphasised that its corporate tax rate, at 28 per cent, was the lowest in the G7 group of leading nations: “As the Chancellor has said previously, we will look to reduce the rate of corporation tax further as circumstances allow.” A source said that there were no plans to change the rules around foreign profits, although he conceded that changes could be made in the future.

Regus, which will continue to trade on the London Stock Exchange, said that the move to Luxembourg would reduce the tax burden on the company, which operates from 900 locations in 71 countries.

In a letter yesterday, George Osborne, the Shadow Chancellor, urged Mr Darling to adopt Tory plans to cut corporation tax to 25 per cent and to simplify the overall tax system. “This would bring greater certainty and proper consultation in place of damaging uncertainty and a lack of consultation we have seen,” Mr Osborne said.

A Treasury aide said that cutting corporation tax to 25 per cent would not help the UK to compete with countries such as Ireland, where the rate is 12.5 per cent. He also said that the Tories’ plans to cut the tax meant reducing business allowances, which effectively meant you were “giving with one hand, but taking with the other”.

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