Julian Smith, MP for Skipton and Ripon, becomes the 70th MP to lend his support to the campaign, which was set up by MP Robert Halfon MP.
Halfon is garnering support in a bid to get the Backbench Business Committee to timetable a parliamentary debate on his motion this autumn.
Halfon’s motion calls for a government enquiry into allegations of oil fraud and market manipulation. He hopes that this will in turn put pressure on the OfT to investigate.
PetrolPromise, which won backing from the leader of Plaid Cymru last month, ultimately wants the non-tax element of the price of fuel reduced.
Its e-petition has now been signed by 1,400 people.