Alistair Darling will signal another tax U-turn this week to prevent a threatened exodus from Britain of multinational companies.

In a speech to the CBI tomorrow, the Chancellor will sound the retreat over moves to tax intellectual property held offshore. The proposal was contained in a Treasury discussion paper on reforms to the way in which earnings from foreign subsidiaries are taxed. It led to a storm of protests from companies fearing that patents and brands held offshore were about to be brought within the reach of the British taxman.

Mr Darling is expected to offer an explicit assurance that the new regime will be revenue-neutral and will pose no specific threat to companies rich in intellectual property. A Treasury spokesman said that the final reform package would be unveiled late next month or in early July.

The backdown comes as Richard Lambert, the Director-General of the CBI, said that the issue of leaving the UK for more favourable tax regimes was on the agenda across business.

In an interview with The Times, he said: “It has become respectable to ask the question. When it was the odd insurance underwriter here or there, it was all a bit remote — but when it gets to the FTSE 100, then you get to a point where boards are saying, ‘shouldn’t we be discussing this?’. We are close to that point, if we are not there already.”

Amid industry concern over tax after several recent controversial moves, Mr Lambert said that tax had reached a “worrying stage”. Britain was more vulnerable than some other countries because it is such an open economy, allowing businesses to move in and out, he said.

Mr Lambert added that while business realised that immediate large cuts in tax were not possible, it had been rocked by the inconsistency of tax legislation and amendments over the past year or so: “For businesses, the rate is important, but so is consistency, clarity and a sense of strategic direction. And that is why the tax changes over the last 15 months have been so damaging. They have made people think: ‘What are the rules around here?’ ”

Mr Lambert’s comments come in the wake of swift changes and then reversals on a number of tax plans such as capital gains, non-domicile taxation and last week’s concessions over the abolition of the 10p rate of income tax.

In a further move to calm corporate nerves, Mr Darling is expected tomorrow to unveil the full membership of a new multinational forum on tax.

The Treasury confirmed yesterday that one member would be Julian Heslop, the chief financial officer of GlaxoSmithKline. The pharmaceuticals industry has been particularly concerned about the implications of moves to change the taxation of intellectual property.

Last month Jean-Pierre Garnier, the outgoing chief executive of GSK, who is a member of the Prime Minister’s International Business Advisory Council, issued a veiled warning to the Government over proposed changes to its tax regime.

Shire, Britain’s third-biggest pharmaceutical company, will incorporate its new holding company in Jersey and hold all board meetings in Dublin to limit its tax bills.

Mr Lambert also gave warning that the Government’s tax take would come under strong pressure because of the troubles in the financial sector. “If you look at where their main sources of tax revenue are, they certainly include the financial services sector . . . The City’s share of the corporate tax base is significant and City bonuses are really important,” he said.

Business confidence fell steeply in the last quarter, according to the latest Business Confidence Monitor from the Institute of Chartered Accountants in England and Wales — the fourth consecutive quarterly fall in confidence.

The heat will be turned up on the Treasury over its series of retreats and climbdowns on key areas of tax policy today when a group of its senior officials appear before the House of Lords Economic Affairs Committee.

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