The amendment was a Fuel Duty Regulator to help combat rising petrol/diesel prices. According to the Western Mail the Regulator would work like this
any extra cash raised for the Treasury from VAT on petrol or diesel as a result of the higher pump prices would be spent on an equivalent cut in fuel duty.
Today the Conservatives proposed changes to combat the rise in petrol/diesel prices. The BBC describes it like this
Shadow chancellor George Osborne told the BBC the party was looking at plans to cut fuel duty when oil prices rise and increase it when prices fall.
So on a nationalist backed vote to lower fuel duty when petrol prices are high the Tories refuse to support, yet three days later they bring out plans to lower fuel duty when petrol prices are high.
Don't you just love party politics?