Appleby, a Jersey-based law firm which operates in several other tax havens, confirmed this week that it was the victim of a data security breach last year.
The firm said it had been approached by the International Consortium of Investigative Journalists (ICIJ) and other media organisations who claimed to have access to the documents.
“A global consortium of left-leaning media organisations” was planning to release the documents in the coming days, which could include the information of some of the UK’s wealthiest people, The Daily Telegraph reported.
A spokesperson for the Revenue said it was aware of the rumoured leak and would look into it if the ICIJ revealed any information.
Appleby said releasing the information may expose innocent parties to data protection breaches.
“Having researched the ICIJ’s allegations we believe they are unfounded and based on a lack of understanding of the legitimate and lawful structures used in the offshore sector.
“Appleby operates in highly regulated jurisdictions and like all professional organisations in our regions, we are subject to frequent regulatory checks and we are committed to achieving the high standards set by our regulators."
After investigating the allegations, Appleby said there was no evidence of any wrongdoing by it or its clients.