David Cameron has likened aggressive tax avoidance to evasion, questioning the morality of the extreme forms of the perfectly legal practice, but points out that changing the law to outlaw such tax planning is not as easy as accountants would have us believe.

Speaking on the first of a three-day tour of India, the Prime Minister told an audience of workers at Hindustan Unilever that the UK government was doing what it could to cut corporation taxes but expected companies to reciprocate by paying their fair share of tax.

He said: 'The message to business should be, "If we are cutting this rate of tax down to a good low level, you should be paying that rate of tax, rather than seeking ever more aggressive ways to avoid it".'

The PM rejected the overly-simplified view that tax evasion is illegal - and "should be pursued by the full force of the law" - while tax avoidance is "is perfectly legal and OK".

'The problem with that is that there are some forms of tax avoidance that have become so aggressive that I think there are moral questions we have to answer about whether we want to encourage or allow that sort of behaviour,' Cameron said.

Addressing the numerous voices from the accountancy profession that have called on the government to simply change the law to make aggressive tax avoidance practices illegal, Cameron said that 'with respect to many friends in the accountancy profession, it is difficult to do that'.