Global firm Appleby today insisted it had done nothing unlawful or wrong in assisting wealthy and powerful clients to manage their tax affairs following the unauthorised publication of client documents.

The leak, coined the Paradise Papers, contains 13.4m documents, reportedly mostly from Appleby, and is the subject of an investigation by nearly 100 media groups.

In a statement on Sunday, Appleby said the coverage was a ‘patchwork quilt of unrelated allegations with a clear political agenda and movement against offshore’. Appleby said the disclosure was caused by an illegal computer hack, perpetrated by an intruder who deployed the tactics of a professional hacker and not someone who works for the firm.

The statement said: ‘We take client confidentiality extremely seriously and we are disappointed that the media has chosen to use information which has emanated from material obtained illegally. This has very little to do with accurate and fair reporting, and everything to do with the pursuit of a political agenda. These journalists will not permit fairness and accuracy to get in the way of their political objectives.’

The data, first obtained by German newspaper Suddeutsche Zeitung and shared with other organisations including the BBC and the Guardian, reveals the tax and financial affairs of hundreds of people and companies, many with links to the UK.

The BBC says many of the stories focus on how politicians, multinationals, celebrities and high-net-worth individuals use complex structures of trusts, foundations and shell companies to protect their cash from tax officials.

Individuals and organisations named include an aide of Canada prime minister Justin Trudeau, U2 frontman Bono and the Queen’s private estate.

Appleby, which has 470 employees operating from 10 offices around the globe, says it has investigated the allegations and insists there has been no wrongdoing.

‘We are a law firm which advises clients on legitimate and lawful ways to conduct their business. We operate in jurisdictions which are regulated to the highest international standards. We do not tolerate illegal behaviour and we reiterate our commitment to responsible business conduct. We are committed to the highest standards of client service and confidentiality. It is what we stand for, this commitment remains unequivocal.’

The disclosure of client’s financial affairs has echoes of a similar release of 11m documents spanning several decades from the Panama firm Mossack Fonseca. The government and the Solicitors Regulation Authority said they were looking into the activities of firms named in the Panama Papers but no action has yet been taken.

Commenting on the papers’ release, Labour’s shadow lord chancellor Richard Burgon tweeted this morning: ’You’re paying your fair share of tax. Why shouldn’t the super-rich - the multi-millionaires and billionaires - do the same?’