Kleinwort Benson said it has hired forensic experts to find out how client data was leaked, following claims by a campaign group that has obtained thousands of account details.

Kleinwort Benson said it has hired forensic experts to find out how client data was leaked, following claims by a campaign group that it has obtained thousands of account details on celebrities and high-profile individuals who banked with the firm in Jersey.

The International Consortium of Investigative Journalists, which has said it is targeting such offshore centres because of the “unfairness” of this activity, rather than necessarily any criminality, has previously obtained data from centres such as the British Virgin Islands, prompting angry responses from such jurisdictions. Loss of client data has hit banks down the years. For example, there have been cases of where banks in Switzerland, for example, suffered loss of client data, which in some cases was put up for sale and bought by public authorities in Germany.

Details on some of the alleged Kleinwort Benson clients – such as actor Mel Gibson, former England footballer Bryan Robson, motorcyclist Valentino Rossi and opera singer Placido Domingo – have been sent by the ICIJ to the UK’s Guardian newspaper. Others are said to be Eddie Jordan, the former Formula One motor racing boss; Oswald Boateng, the renowned tailor, and Sir Edward Evans-Lombe, a retired High Court judge and Norfolk landowner.

In a statement, Kleinwort Benson said: “We are aware that the Guardian has published an article about the private and entirely legal financial affairs of a number of individuals based on what they claim to be `leaked offshore clients lists from Kleinwort Benson obtained by the International Consortium of Investigative Journalists.’  We take client and data confidentiality extremely seriously and are understandably concerned to understand how confidential client information may have been obtained.  We will take all necessary steps to protect client confidentiality and have engaged external forensic counsel to conduct an urgent investigation into the source of any leak of confidential client information.”

Separately, Jersey Finance, the organisation that represents the island's financial sector, sought to defend the jurisdiction's reputation.

‘There is nothing illegal or untoward about anyone, whether they are a celebrity or not, having a bank account or trust in a well regulated jurisdiction such as Jersey. There are many perfectly legitimate reasons for doing so and the reports in the Guardian appear to have no substance. Of concern is that confidential information about bank accounts has been leaked and I welcome the news that Kleinwort Benson is to conduct an investigation into this," Richard Corrigan, deputy chief executive at Jersey Finance, said in a statement.

The ICIJ has not stated how, or from whom, it obtained the information.

In its statement issued earlier this week, the ICIJ said: “The individuals include donors to the British government, which has been outspoken against tax havens, and some of the most prominent people in British life.” The group said it allowed the Guardian newspaper – which has published such material before – to analyse “more than 20,000 of the names, all of whom had dealings with a discreet Jersey, Channel Islands branch of Kleinwort Benson”.

The group previously published secret internal records of offshore companies in the British Virgin Islands in 2013.

“We make this information available not because what we found is illegal but because we think most people would think it unfair. Tax havens allow some people to play by different rules,” ICIJ director, Gerard Ryle, said.