David Hartnett, the head of the HMRC in 2011, told MPs that his department was in possession of records from the Swiss subsidiary of a major UK bank, containing the names of potential tax dodgers.When Hartnett faced MPs four years ago, Stephen Green, the former chairman of HSBC was acting as trade minister"I think the whole nation probably knows that our department has a disc from the Swiss - from the Geneva branch of a major UK bank - with 6,000 names, all ripe for investigation," Hartnett is shown as saying by transcripts.In a conversation with the Labour MP Tom Blenkinsop, Hartnett said: "We have hundreds [of people] under investigation, some of them under criminal investigation, and we are about to challenge another 800. Then we will industrialise the process, challenging 1,000 at a time, with a view to having all those who need challenging challenged pretty quickly."Hartnett, who told MPs HMRC had got hold of the disc containing the records in 2010, did not name HSBC directly the bank was identified in newspaper reports at the time.HMRC former boss' statement contradicts what the government said earlier on Tuesday, when a spokeswoman for the Prime Minister said MPs had been unaware of tax evasion at HSBC's Swiss division until news emerged on 8 February."No government minister had any knowledge that HSBC was involved in wrongdoing in regard to its Swiss banking arm," the spokeswoman said."We have no record of any government minister being made aware by HMRC of any alleged wrongdoing by HSBC employees."