The more on-the-job mileage the employees do, the larger and more powerful a car the staff members are entitled to.
``There are, of course, advantages to the individual in having a lease car, especially as it is available for private use,'' says an explanatory booklet sent to The Independent by a disgruntled staffer.
``Employees will be free of the worry of road tax, insurance, maintenance and unexpected and expensive repair bills.''
The agency has no mileage allowance for using bicycles on work journeys, nor any loan scheme to encourage bike purchase. It has 1,715 of its own vehicles and only a few dozen bicycles used by its water bailiffs.
It gives its staff no incentives or instructions to use public transport rather than cars. Furthermore, a growing number of the watchdog's many offices in England and Wales are in edge-of-town or rural locations, badly served or completely missed by buses and trains.
The leasing scheme is open to any member of staff doing at least 5,000 miles a year on business. The employee has to pay 29 per cent of the leasing cost, and gets a mileage allowance for work-related journeys. He or she can use the car for up to 15,000 private miles each year and can take it overseas.
As well as covering insurance and garage bills, the lease scheme offers a replacement in the event of breakdown, theft or accident. Staff who join get a new car of their choice, which they can swap for another new vehicle after four years or 80,000 miles.
The agency sees the scheme as a money-saver - it is cheaper than letting employees use their own cars for work journeys and claiming a higher mileage allowance. It also ensures that staff drive around in vehicles with smog- curbing catalytic converters rather than badly tuned, highly polluting old bangers.
To seduce staff members into joining, it is offering a ``holiday'' on their share of the lease costs of up to 14 months, worth a saving of more than pounds 1,000. So far up to 2,000 staff have joined, but about the same number still use their own cars.
The most questionable part of the scheme is the way it allows staff with the highest mileage to have the most gas-guzzling, greenhouse-gas producing cars. Those doing at least 15,000 miles a year are entitled to a petrol engine up to 2,000cc or a diesel up to 2,500cc. Between 15,000 and 10,000 miles the maximum is an 1,800cc petrol engine. Under 10,000 miles it iss 1,600cc petrol, or 1,905cc diesel.
A spokeswoman for the agency said it felt staff spending long hours on motorways needed larger, more powerful cars. ``This was done on comfort and safety grounds.''
She said that in monitoring and regulating industry, rivers and waste dumps scattered around the country, agency staff could never do their jobs using only public transport and bicycles.
But some staff have been writing to the agency's internal paper to complain about what they see as pro-car policies. Douglas Paulley, from the North East Region, says it ``seems hypocritical and unnecessary''.
But in the same latest issue the agency's director of personnel, Giles Duncan, responds in a way which will have all cyclists gritting their teeth. ``I admire people who cycle to work - they must realise, though, that not everyone can. Nor are we going to send our pollution inspectors wobbling off on a bike to visit ICI. So let's keep our sense of proportion.''