Tens of thousands of new UK companies have been registered over the past two months, double the normal rate, as taxpayers try to get round a Treasury crackdown intended to bring in an extra £1bn of revenue over the next three years.

New tax rules will next month close a loophole used by 250,000 temporary IT specialists, engineers, builders, nurses, teachers and others, who can reduce their tax bills by as much as 30 per cent by being paid through a "managed service company".