Up to £4bn in potential tax revenues could be lost to the UK and scores of developing countries if the government presses ahead with plans to relax its anti-tax haven laws.

That's the fear of several NGOs over the Controlled Foreign Companies (CFC) rules proposed in the 2012 Finance Bill and due to come into force in January 2013.

This could incentivise multinational corporations to shift profits into tax havens and "have a significant detrimental impact on the tax revenues of developing countries", according to a report by the International Development Committee (IDC).

MPs on the committee have called on the government to conduct an urgent analysis of the likely impact of the changes.

Under the current system, if a UK-owned corporation reports profits in jurisdictions with lower corporate tax rates than the UK, the UK government can impose an extra tax charge on the corporation to 'make up the difference'. Profits shifted from developing countries into tax havens, therefore, would still incur tax at UK rates.

But under the new rules, the UK will only be able to impose this extra levy if the profits in question have been shifted from the UK.

An ActionAid report said: 'The proposals will eliminate a significant deterrent that discourages UK-based companies from shifting profits from developing countries to tax havens. We estimate that the reforms may cost developing countries as much as £4bn.'

The charity believes the new tax loophole would be "a huge step backwards for developing countries" and "a major contradiction in the UK's international development policy".

It continues: 'Some multinational businesses, including many involved in high profile tax avoidance disputes, have lobbied hard to make this new loophole as big as possible. Some 30 companies, with a total of well over 3,000 subsidiaries located in tax havens, lobbied for the changes through advisory groups set up by the Treasury.'

But while the UK government has disputed the £4bn figure, it has agreed that there will be a cost to developing countries, the IDC says.

Stephen Relf, a specialist corporation tax editor at CCH, said: 'Following the comments made by the IDC, and the recommendations made by the IMF and other bodies to the G20 countries, the government is now under pressure to consider the impact of future changes in tax law on tax revenues in developing countries.

'This wasn't done in the case of the CFC rules and it may cost developing countries dearly. Tax avoidance isn't limited to the avoidance of UK tax and the Government will need to be aware of this going forward.'

A recent joint report by the IMF, OECD, UN and World Bank argued that where domestic policy reforms were likely to impact on revenue flows to developing countries, a 'spillover analysis' should be conducted to discover the magnitude of such impacts.