The government continued its crackdown on corporate tax avoidance in yesterday's Budget but left companies uncertain about a proposed principles-based regime on tax issues.

The government has been rapidly closing tax dodges after introducing a system in 2004 that obliged advisers to inform it of tax-mitigating approaches they intended to employ. This has given a head-start in tackling potential issues, advisers say.

Companies have been waiting for the government to come forward with wide-ranging principles-based regime for tax avoidance. This, the Treasury confirmed yesterday, has been delayed until the 2009 Finance Bill. Instead, the government targeted several specific practices it regards as tax dodges, many of them used by large corporations.

Prime among them is the creation of "disguised interest", an approach that allows companies to receive interest in the form of non-taxable distributions.

It is clamping down on arrangements where companies offset UK taxes against credits for overseas tax even though they never paid it.

The Treasury is also seeking an end to the practice of corporation tax avoidance, where companies adopt different accounting treatments within the same group of convertible debt.

"This has been going on for a long time," said Martin Bell, associate partner at accountant Deloitte, who sees the measures as another step on the road to ending more aggressive corporate tax planning. "You will see tax rates for large corporates gradually going up," he said.

There are additional measure to stop businesses hiring plant or machinery in ways that exploit differences in how manner rentals that are paid and received are taxed in order to generate an artificial tax loss.

Another attack has been made on the practice of diverting profits from the UK so the company can escape domestic taxes.

This has been achieved in the past by arranging for an offshore trust to own more than 50% of the shares in an overseas company. The users of the scheme claim the company is not controlled by UK residents even though the UK residents who hold the remaining shares retain the right to receive all the company's profits. Other schemes allow interest to accrue in a partnership where the holding company claims it does not form part of the group income.