The Inland Revenue and Customs and Excise are drafting in an extra 150 staff to crack down on tax evasion by illegal gangmasters.

The Revenue said it is committed to tackling the problem vigorously and has been given £5 million over the next three years to set up a network of specialist teams.

The Transport and General Workers’ Union which has been investigating the issue, estimates there are up to 5,000 gangmasters in the UK, with about 20 per cent operating illegally.

The Revenue already has 18 staff in two regional specialist teams investigating “non-compliance” relating to employer, corporation tax and income tax issues.

A further 50 revenue staff will be in place by the end of the month with another 20 joining the teams probing illegal gangmasters later in the year.