Gordon Brown demands garages slash petrol prices

I noticed where I live yesterday that Morrisons and Shell both had unleaded down to 99.9p a litre, whereas Tesco it was still at 106p. But its a free market isn't it? If people want to pay more for their petrol as it is more convenient to fill up when they do their main shopping at Tesco than go elsewhere, I don't quite see what that has to do with the government.

I imagine Gordon Brown is saying this just for an easy headline-grab.