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Claims that banking giant HSBC helped rich clients dodge tax started a political firefight in Britain as the main parties sought to blame each other for not acting.
Prime Minister David Cameron's Conservatives appointed former HSBC chief executive Stephen Green to the House of Lords in 2010, where he served as a trade minister.
But the main opposition Labour party, hoping to take power after May's general election, faced allegations that it had not clamped down on tax dodging when it was in government until 2010.
This covers the period when HSBC's Swiss private bank is accused of helping clients evade taxes on accounts containing $119 billion.
The row highlights the complex task both parties face in casting their relationship with big businesses ahead of the May 7 general election, in which opinion polls suggest they are virtually neck-and-neck.
Cameron's centre-right Conservatives are traditionally seen as more in tune with big business but were labelled 'the party of Mayfair hedge funds and Monaco tax avoiders' by Labour last week over a tax loophole for hedge funds.
Meanwhile, centre-left Labour's policies have drawn criticism from several business leaders who say they could damage the economy and contrast leader Ed Miliband's rhetoric with the business-friendly Labour administration under Tony Blair from 1997.
Green, HSBC's chief executive from 2003 before becoming chairman in 2006, declined to comment on the claims when questioned by the BBC Monday.
Labour urged finance minister George Osborne to explain how Green was appointed.
"Once again the Tories have been exposed as unable and unwilling to take real action on tax avoidance -- little wonder that under them the tax gap has risen year on year," shadow finance spokeswoman Cathy Jamieson said.
The government hit back at Labour, saying the party had failed to act.
"I do have to make the point that there was a lack of grip in this area and a lack of progress in dealing with tax cheats," junior finance minister David Gauke told BBC television.
He also denied that there was "any suggestion or any evidence" that Green was directly involved in the activities of HSBC's Swiss private bank.
The claims against HSBC arise from files obtained by the International Consortium of Investigative Journalists (ICIJ) -- a network of investigative reporters -- via French newspaper Le Monde.
