Drivers of the biggest and most polluting vehicles are to see car tax almost double to �400 by April 2008, Chancellor Gordon Brown has said. The rise accompanied a 30% cut in vehicle excise duty (VED) for some of those which emit the least pollution. Mr Brown also promised to work towards special mortgages for energy efficient upgrades on homes, and to abolish stamp duty on some zero-carbon homes. But critics said Mr Brown was not doing enough to confront climate change. "There's some good measures in it, but it doesn't go far enough at all," said Dave Timms of campaign group Friends of the Earth.