Millions of pounds of the Queen’s private money is invested in offshore funds in Caribbean tax havens, a huge leak of financial documents referred to as the “Paradise Papers” has revealed.

The documents show that the Duchy of Lancaster, which manages investments for the Queen’s £520m private estate, invested around £10m in the Cayman Islands and Bermuda-based funds.

They also show that the monarch holds small investments, via funds, in businesses including off license chain Threshers and BrightHouse, which has been accused of exploiting people with mental health problems and learning disabilities in order to sell its products.

The funds have not previously been disclosed in official Palace accounts. There is no suggestion that they are illegal.

The revelation is likely to increase pressure on the Royal Family to increase transparency over where and how they invest their wealth.

A spokesman for the Duchy of Lancaster said: "We operate a number of investments and a few of these are with overseas funds. All of our investments are fully audited and legitimate."

The 13.4 million documents lay bare how thousands of rich and powerful individuals invested vast sums of money in murky offshore structures.

They reveal that Donald Trump’s Secretary of Commerce, Wilbur Ross, owns a stake in a firm linked to Russian businessmen who are the subject of US sanctions.

The papers were obtained by German newspaper Süddeutsche Zeitung and are being analysed by 100 media organisations across the world.

The papers come from the company registries of 19 tax havens, and two offshore service providers. They were released less than two years after the leak of the Panama Papers caused shockwaves by exposing how dozens of well-known figures were hiding wealth in offshore funds.

In total, 1.4 terabytes of data have been released via the Paradise Papers – the second biggest leak of data in history. Only the Panama Papers were bigger, at 2.6 terabytes.

Lord Ashcroft, the Conservative peer and a major donor to the party, was also named in the papers.

Labour's Shadow Chancellor, John McDonnell, said: "These are deeply worrying revelations. Despite all the Government's claims of cracking down on tax dodgers, this evidence confirms that tax avoidance is clearly continuing on an industrial scale.

"Either the Prime Minister or the Chancellor needs to explain how this scandalous behaviour has been allowed to go on unaddressed for so long and what action is to be taken now."

A government spokeswoman said: "Since 2010, the Government has secured an additional £160bn, more than the annual UK NHS budget, for our vital public services by tackling tax avoidance, evasion and non-compliance.

"This includes more than £2.8bn from those trying to hide money abroad to avoid paying what they owe. There are 26,000 HMRC staff tackling tax avoidance and evasion, and we have provided an extra £800m to fund their efforts.