Apparently Gordon Brown helped a lot of us to choose a "greener" car by telling us they were not as polluting as petrol.

He knew all along that they WERE much more polluting but thought penalising the drivers would not go down well with the voters. This "Dash for Diesel" started in 2001 and was pushed even more in following years.
At the time only one in seven cars was a diesel. Now, as a result of the Labour policy, it is one in two.

So when they tell you about their green credentials just don't believe them. They are opportunists.

http://www.bbc.co.uk/news/uk-politics-41985715