Prime Minister David Cameron has lost his second minister in two days, as Lord Marland stepped down as minister for trade.
The peer's resignation comes just a day after the departure of Lord Strathclyde as Leader of the House of Lords.
A Downing Street spokesman said: "Lord Marland will be stepping down as a minister in order to focus on his role in trade promotion."
Lord Marland of Odstock, 56, is a businessman and former Conservative Party treasurer who was made a life peer in 2006 and served as an opposition whip and spokesman in the Lords.
He was treasurer for Boris Johnson's successful campaign for London mayor in 2008 and made an unsuccessful bid for chairman of the England and Wales Cricket Board in 2009.
He was appointed to a junior ministerial job in the Department of Energy and Climate Change after the formation of the coalition Government in 2010 and moved to the Department for Business in last year's reshuffle.
He travelled the world to bang the drum for Britain as Mr Cameron's trade envoy but garnered bad headlines by joking on a trip to Mozambique last year that he was "just trying to keep the suntan up".
His resignation comes a day after Mr Cameron and Deputy Prime Minister Nick Clegg tried to inject some momentum into the coalition Government with the launch of a mid-term review.
The loss of the Conservative minister was announced just hours after Mr Cameron told Tory MPs in a Westminster meeting that it was time to roll their sleeves up in preparation for the 2015 general election campaign.
On Monday, Mr Cameron lost one of his most experienced Cabinet ministers when Lord Strathclyde announced he was quitting to pursue business interests.
Labour vice-chairman Michael Dugher said: "To lose two ministers in two days shows David Cameron's Government is in total chaos.
"Just one day after their botched relaunch, even people at the very heart of Cameron's Government are losing faith and abandoning ship."