An email HSBC whistleblower Herve Falciani says he sent Revenue and Customs about alleged tax evasion comes to light.

Mr Falciani says his email warned tax collectors that thousands of British clients of an HSBC subsidiary in Geneva were using the bank to hide money. The email, from 2008, has been uncovered by Le Monde and seen by the BBC.

Revenue and Customs and the Crown Prosecution Service (CPS) are facing criticism over the fact that only one conviction has been secured using information, leaked by Mr Falciani, relating to almost 7,000 UK individuals and organisations with accounts at HSBC in Geneva.

This information came from the time Herve Falciani worked for the bank in the IT department from 2006-08. He later passed this to the French tax authorities, sparking an investigation into allegations of tax avoidance and evasion.

HMRC has said it has no record of receiving an email or phone call in 2008.

It was given files about British residents from the French authorities in 2010, and has used these to pursue around 1,100 individuals and organisations, securing £135m in tax, fines and interest payments, but just one criminal conviction.

Herve Falciani talks to Channel 4 News

Herve Falciani told Business Editor Siobhan Kennedy on Thursday that Spain’s justice department had more data than the British authorities. “They have much more data than the UK have and it could be a good opportunity for the department of justice or the UK department of justice to collaborate. They (the French) have more detail than you and less than Spain.”

Mr Falciani said “hundreds” of other banks were involved in the same activities as HSBC. He said he called HSBC in 2008 and was told to fill out a form relating to every HSBC client whose details he held. When he explained this would not be possible, he was told: “I’m sorry, I don’t know what to do.”

HMRC Permanent Secretary Lin Homer said three cases were passed to the CPS, which chose to prosecute only one of them. The allegations surfaced again this week after the Guardian and BBC Panorama analysed information from the files.

Former director of public prosecutions Keir Starmer, a Labour parliamentary candidate, said criminal prosecution, rather than civil penalties, should be used in allegations of tax evasion.

He told the BBC Today programme: “Tax evasion involving dishonesty is not sort of fraud, it is fraud, it is criminal and should be treated as all other fraud is treated. In my view, criminal prosecution ought to be the default position for tax evasion, not civil penalties.”

At a meeting of the Commons public accounts committee on Wednesday, Ms Homer was asked if HMRC had received data from Mr Falciani in 2008. She responded: “Not to my knowledge.”

A spokesman for HMRC said: “HMRC has not found a record of receiving an email or any phone call from Mr Falciani in 2008. As Lin Homer said at the PAC, we are looking into whether HMRC received an email or phone call, and if we did what then happened.”