Bookmakers and casinos have avoided paying around £1bn in UK tax since 2009 by routing online and phone bets from the UK through subsidiaries based in overseas tax havens, according to a report by The Independent.

The estimated £250m a year, which football, racing and poker betting operators save by offshoring online gambling, amounts to far more than the recent highly publicised cases of tax avoidance by Starbucks and Amazon.

Bets placed via websites and phone lines in the UK are regulated and taxed in British overseas territories such as Gibraltar, Guernsey and the Isle of Man. This means operators are able to replace the UK gambling duty of 15% on gross profits with an effective rate of duty of less than 1%.

In a statement, William Hill, which saves an estimated £37m annually in betting duty, vigorously denied it was 'engaged in any avoidance scheme or artificial tax structure'.

Ladbrokes, which saves around £18m annually, said it had only moved offshore reluctantly 'to survive and compete'.

The government is currently consulting on a new gambling duty centred on 'point of consumption', which would tax bets where they were placed, rather than at the 'point of supply', which is where they were taken. However, any changes are not likely to be introduced before December 2014.