UK 'is losing £4bn tax offshore'

EU rules allow UK residents to declare interest earned overseas or to have 15% withheld from interest in the country where the account is held.

Separately, a report says MPs are calling for a review into the use of havens by taxpayer-backed banks.

Under the EU rules, three-quarters of the 15% in tax on interest that is withheld offshore is eventually paid to the UK government.

But this means that the effective amount collected by HM Revenue and Customs was 11.25% - rather than the 40% which would typically be paid, the TUC says.