Speaking exclusively to Accountancy Age, chief financial officer Jon Symonds admitted that, although there were aspects of the rules that would benefit AstraZeneca, 'Sarbanes-Oxley has all the hallmarks of using a sledgehammer to crack a nut'.

He added that the costs of complying with the act clearly outweighed the benefits and that, for AstraZeneca, 'we are talking in the tens of millions'.

But Symonds said: 'AstraZeneca would not abandon the US market even if it were easier to do so. We remain committed to the US market: we have a strong presence there,' he said.

At least 60 European companies, including 25 from the UK, are set to withdraw their US listings because of Sarbanes-Oxley, according to comments made by CBI director general Sir Digby Jones last week.

The figure would be even larger if not for the 300-shareholder rule that the Securities and Exchange Commission has imposed. Companies cannot deregister from the SEC, and thus avoid Sarbanes-Oxley, unless they have fewer than 300 US shareholders.

SEC chairman William Donaldson hinted in London last week that this rule would be reviewed to make it easier for companies to delist.

In an attempt to see off an exodus, New York Stock Exchange chief executive John Thain argued that the impetus to leave the US markets would fade as European legislation moves towards the American model.

'Sarbanes-Oxley will get picked up by European regulators,' said Thain. 'The regulatory arbitrage that the European exchanges are marketing at the moment will not last very long.'

However, a source close to UK regulators said: 'Quite frankly they don't know what they're talking about. There are huge differences in the way Sarbox is interpreted and applied in the US and the way the rest of the world looks at these things.'