Since 2011, €5.5bn held in secret bank accounts abroad has been ‘legalised’ by the tax office, generating over €600m for the treasury, according to the tax office’s latest report.

Seven out of 10 people who had illicit savings in foreign accounts were over the age of 60, the report states. On average, they had €400,000 on their accounts.

Most money was held in accounts in Switzerland, Luxembourg and Belgium.

When the government first announced it would tackle secret bank accounts, there was no fine for people who confessed. Now, however, people have to pay a 60% fine as well as tax on their secret savings.

The tax office has also set up a special team to focus on people with assets of more than €25m. The 10-man team will focus on analysing the tax returns of very wealthy individuals, thought to number about 2,000.

Junior tax minister Eric Wiebes told BNR radio the aim of the new team is to provide ‘better service’ rather than to make sure they are not evading taxes.

However Ton Apeldoorn, director of a financial research agency who has worked for the tax office investigation department for years, said Wiebes is talking nonsense.

‘It is all about controls,’ he said. ‘If very rich people have questions about their tax, they are solved by a tax advisor or lawyer.’