The UK authorities were already in possession of detailed evidence about wrongdoing at HSBC’s Swiss bank when David Cameron made the executive chairman of its parent bank, Stephen Green, a government minister, the Guardian has established.

French tax authorities passed leaked Swiss data containing 6,000 British names to Her Majesty’s Revenue and Customs in May 2010. Lord Green’s appointment as a Conservative trade minister in the House of Lords was made public a few months later.

Green was executive chairman of the HSBC bank group from 2006 to 2010. The bank’s current management now admit serious “compliance and control failures” occurred at the Swiss bank before January 2011 when HSBC’s current chief executive, Stuart Gulliver, took over.

HMRC is also facing questions about its handling of the leaked Swiss data. Its then head of tax, Dave Hartnett, went on to work for HSBC as a consultant after his retirement two years after the data was handed over. The UK has taken no legal action against the bank despite the evidence in the leaked files of wrongdoing, and only one individual has faced prosecution.

In France, HSBC is being prosecuted for what the authorities call organised “money-laundering” while Belgian prosecutors charged the Swiss bank on suspicion of helping clients evade tax using offshore vehicles.

France has recovered £188m in taxes and fines from a list of 3,000 clients and Spain has recovered £220m, also from 3,000 clients. The UK, by contrast, has recovered just £135m from a list of 6,000 clients in a series of secret deals that kept names out of the public domain. Many evaders were offered light penalties of only 10% of tax due, plus immunity from prosecution. The Guardian has pieced together a timeline of the material’s journey into possession of the UK authorities.

Documents disclose that in early February 2010 news was first passed in confidence, under international tax information-sharing agreements, that the French government had obtained a sensational leak from HSBC’s Swiss bank.

Facebook Twitter Pinterest HSBC files: how secret Swiss account data detailing misconduct came to light

The leak had come from HSBC’s IT technician in Geneva, Hervé Falciani, from whom French police seized the incriminating data. France offered to pass on the contents of the so-called “Swiss disc” to HMRC. On 11 February 2010, Hartnett went to see HSBC at its London headquarters, according to his hospitality register. The Guardian asked Hartnett what was said at that meeting about the Swiss leak. He said: “Lunch was sandwiches, fruit juice and water. You will have to ask HMRC for details of what was discussed.”

In May 2010, HMRC was handed a reconstructed UK version of the data by the French. But while tax inspectors began ploughing through their evidence at their London headquarters, a change of British government was taking place.

Cameron’s Conservative-led coalition came to power. A couple of weeks later, it was reported that Green would step down from his £1.25m-a-year HSBC job, and by August Cameron was reported to have persuaded him to take on the post of trade minister.

“In Stephen we will be appointing a minister with a long career as a leading international banker,” the Lib Dem business secretary, Vince Cable, said in a statement issued after the announcement: “One of the few to emerge with credit from the recent financial crisis, and somebody who has set out a powerful philosophy for ethical business.”

A source close to Cable said the welcoming remarks on Green referred to HSBC’s position as the sole major UK bank not requiring a bailout in the financial crisis, and to Green’s writings and speeches on ethical business.

Contacted by the Guardian on Monday as to his view on his former junior minister in the light of the HSBC revelations, Cable said: “We simply don’t know at present if Lord Green was aware of or condoned these practices.”

HSBC now accepts that customers, many of them British, had been taking advantage of the secrecy on offer to set up undeclared Swiss accounts. Yet at HMRC it was decided that prominent British individuals found to be cheating on their taxes would not be prosecuted, a process which would have led to them being named and the facts coming out.

Hartnett has defended the secret tax repayment deals. “There was never an intention to deliberately use taxpayer confidentiality to hide the identity of HSBC clients.” Lin Homer, the overall head of HMRC, also defended this non-prosecution approach before the UK’s public accounts committee in 2012, as a cheaper source of revenue. “The important thing is to get the money in,” she said.

But the committee which questioned her was unaware of the mountain of evidence that existed of wrongdoing at HSBC itself. Margaret Hodge, the committee chair, said on Monday: “I am no lawyer. But it seems to me absolutely clear that we’ve got an open and shut case of a systemic policy to support hundreds of people in avoiding paying their tax. And I think the tax authorities here in the UK, HMRC, should look to challenging the bank in the courts.”

Other European countries have launched prosecutions against individual clients of HSBC’s Swiss bank since being passed the files. In France last year, Arlette Ricci, heir to a perfume fortune, became the first of some 50 clients to be hauled into court, where she denied tax fraud.

In Belgium, a score of Antwerp diamond traders were raided and the bank itself was charged. In the US, not only have individual HSBC tax evaders been prosecuted, but in a separate investigation, the bank narrowly avoided the loss of its licence in 2012 for allowing drug cartels to launder millions of dollars through the group’s Mexican division.

Assistant attorney general Larry Breuer said a criminal prosecution would have cost too many jobs and destabilised the banking system. HSBC was allowed to settle with some harsh publicity and cash penalties of $1.9bn.

Hartnett retired from HMRC in 2012. Six months later, while the Swiss disc was still under investigation by his old department, he went on the payroll of HSBC itself. He was being hired, the bank said, to advise on its reformed anti money-laundering measures.

The watchdog which vets such moves from government jobs into the private sector, the advisory committee on business appointments (ACOBA), was assured, it says, that Hartnett “had official dealings with HSBC over a number of years, but that these contacts were no more significant than the contacts he had with other banks operating in the UK”.

Hartnett denies that this version of events was misleading. He said: “I made a detailed application to ACOBA referring specifically to the investigation of customers of HSBC Geneva. My application was reviewed and countersigned by the HMRC chief executive.”

He adds it was “HMRC’s chairman who took an interest in the work of the Enforcement and Compliance directorate. I did not then, or at any other time, get involved in decisions about HSBC investigations. You are therefore wrong to associate me with accountability for performance in this area.”

HMRC’s chairman at the time was a business outsider, Mike Clasper, the former chief executive of airports operator BAA. He did not respond to requests for comment.