The early morning "school run" is responsible for almost a third of polluting traffic on the roads, the Government warned on Friday.
The Department for Education and Employment was now looking at the problem and wanted targets to increase the levels of walking, cycling and bus use, said Education Secretary David Blunkett.
He called for an end to "the vicious cycle in which unsafe roads lead parents to prefer driving their children to school", saying 24 000 people were now estimated to die prematurely each year because of air pollution.
Poppycock, said the Conservative shadow transport minister, Bernard Jenkin who stated the Government had to "get real" on transport.
"Parents rightly care about their children's safety. Lecturing school-run mums and dads that they should make their children walk or ride their bikes to school completely ignores these concerns, and the lack of real alternatives.
He accused Transport and Environment Secretary John Prescott of failing to combat the problem of traffic congestion surrounding schools.
"It's all well and good Labour saying that the National Cycling Strategy or `Safe Routes to School' hold the key, but these policies were launched by the last Conservative Government. Labour has done nothing since then."
[Factual note: Safe Routes to School was not a Tory government initiative: it started with a grass roots campaign which was later picked up and amplified by Sustrans]
A spokesman for Sustrans said: "Sustrans welcomes the Government's interest in this area. However this requires investment to provide bike lockers, security and of course changes in the road system and firmer enforcement of speed limits."