A Conservative MP blasted an Office of Fair Trading (OFT) inquiry into petrol prices as "limp-wristed and lettuce-like" in the wake of price-fixing allegations.
Harlow MP Robert Halfon, who has campaigned for cuts to duty and greater transparency in the market, said despite the Commons unanimously calling for a thorough probe into petrol pricing, the regulator failed to spot any of the allegations currently under review.
Mr Halfon said: "Do you not agree that what happened was the OFT carried out a limp-wristed, lettuce-like inquiry when they should have done a full 18-month inquiry into what has been going on?"
Energy Secretary Ed Davey defended the OFT as an "independent body, a strong body", which has powers to determine its own investigations.
Mr Davey made a statement updating MPs on the launch of a European Commission investigation into oil companies BP, Royal Dutch Shell and Norwegian company Statoil.
More top news
1,209 people were found guilty of 'trolling' offences in 2014 - and 155 have been jailed.
Critics are ambivalent to this year's slate of winners, who were picked in part by American directors Joel and Ethan Coen.
1.5m European citizens will miss out on the chance to vote on whether Britain stays in or quits the EU.