Nick Clegg and Vince Cable have been urged to "come clean" about their professional connections to firms engaged in fracking by a Labour MP.
Ian Lavery, who serves on the Commons Environment and Climate Change committee, said: "It’s really a concerning fact because they’re in positions to move, shape and develop policy."
"They need to come clean, put their cards on the table and declare an interest particularly in the really live issue on shale gas and its potential development in the uk, particularly when fracking is causing great concern up and down the UK."
According to Channel 4 News, Clegg worked "representing clients including the car rental company Hertz and the BG Group". The oil and gas firm BG Group is known to have heavily invested in shale gas exploration.
The Liberal Democrats' links with BG Group caused controversy in 2011 over an alleged "cash-for-access" scandal. As part of a £1m party fundraising programme, the Liberal Democrats were found to have offered business lobbyists £25,000 to join the exclusive 'Leader's Forum', which offered dinners with Nick Clegg.
The 'Leader's Forum' was promoted to lobbyists at a launch event, attended by Treasury chief secretary Danny Alexander and Vince Cable alongside representatives of the Tobacco Manufacturers' Association, the Tobacco Retailers' Alliance and the BG Group, as reported by PR Week.
Meanwhile, Cable served as Shell's chief economist in 1995 to 1997, which also engages in fracking. In 2012, the Huffington Post UK revealed a letter describing him as "the contact minister for Shell". In recent weeks, the LibDem business secretary has mounted a robust defence of the coalition's "reasonable" decision to award tax breaks to fracking firms.
The government's pro-fracking stance provoked derision from Lavery, who said: "Clegg and Cable are up to their neck in energy policy but is it a case that they’ve been paid for it in a previous life and they’re delivering on what they’d say they’d deliver?"
"The potential reliance on shale gas and the thought that this could be the panacea for all the uk’s energy problems is an absolute pie in the sky and cloud cuckoo land."
In response to Lavery's attack, a Liberal Democrat spokesperson told the Huffington Post UK: “This is complete and utter tosh. To suggest that because someone worked for someone decades ago that they have influence over government policy is breathtakingly desperate.”
Fracking has consistently attracted controversy. Earlier this week, anti-fracking protesters were arrested in Balcombe while Tory peer Lord Howell suggested last week taht fracking should happen in the "desolate" North East and the "unloved" North West of England.
Green Party leader Natalie Bennett said that the senior LibDems' links were a sign of the "pervasive" reach of the fracking industry.
"I know there are lots of Lib Dem members and supporters who are shocked and dismayed that their party leaders are not just accepting fracking, but enthusiastically promoting it, with Energy Secretary Ed Davey recently deliberately repeating the phrase that he 'loves it'.
"I'm not surprised that many people are highlighting the fact that the two most senior figures in the party have prominent links to the oil and gas industry in their employment past.
"The pervasive reach of the oil and gas industries (and a number of other industries, from tobacco firms to supermarkets) through our political system is a cause for grave concern.
"Voters have good cause to ask about whose interests are being represented."