Dear John Gummer: All revved up and nowhere to go. Why doesn't the Secretary of State for the Environment do something about drivers who just sit there with their engines running?

I know you have a tough job. I do sympathise, really. That's why I'm offering a magically simple solution to the problem of our environment - one that is slowly choking us to death and turning our children into asthmatics: I'm talking about exhaust fumes.

I'm sure you are familiar with this summer's horror statistics. If you get out of your ministerial car and walk around our cities you'll find it difficult to breathe. This is not just caused by people driving around; it is caused by people not driving at all.

Take a walk down Shaftesbury Avenue one evening. Rows of coaches sit there, engines rumbling, belching out exhaust smoke for three hours while their passengers watch Les Miserables and their drivers snooze in the front seat. Visit our historic city centres and tourist sites; they've been turned into smog zones.

Coaches are not the only culprits. I recently had a play performed in the Liverpool Playhouse. If you stepped into the square outside you could hardly breathe, the air was so poisoned by the rows of gently throbbing taxi-cabs - 20 of them - which sat there empty.

Then there are those people who sit in their executive cars, talking on portable phones. The other day a man sat outside my house for more than an hour, with his engine running, and plumes of exhaust billowing into the street while he chattered away. When I remonstrated with him he told me to bugger off.

And then there are the chauffeurs. I once talked to a one sitting in his Jaguar blithely unaware of the fumes he was causing. He said it was part of his training; cars had to be ready for a quick getaway - as if he were in Dodge City rather than waiting for some insurance director and his wife to come out of the Grosvenor House ballroom.

Why does nobody speak about this? Are we too diffidently British and frightened of being snapped at? I have a suspicion it is linked to some deep-seated male insecurity - men are worried that if they switch off their engine they will never rouse it back into life.

There is a simple solution to this: get people to switch off their engines when their cars are parked. You have the power to do this. Legislation could be brought in. On-the-spot fines could be introduced. Friends of the Earth has already targeted bus stations, where the vulnerable - the very old and the very young - have to wait in clouds of exhaust smoke from idling buses.

In Switzerland, vehicles are required to switch off their engines when waiting at traffic lights. Why don't we go one stage further and do what I have suggested? For once, we could lead the way. And maybe - just a thought - you could start with the fleet of ministerial cars. Just to show you're willing.

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