Motorists in Oxford will be hit with £40 fines - and could face court action - if they leave their engine running unnecessarily for just a matter of minutes.

In a bid to tackle the city's air pollution problem, city council enforcers have been briefed to clamp down on drivers who leave their engines idling.

The Town Hall has been equipped with powers to fine motorists for engine idling since 2002 - but enforcement in Oxford will now start on April 28.

Drivers of vehicles caught idling - even environmentally-friendly hybrid cars - will be asked to turn off their engines.

If they refuse, they will be handed a fixed penalty notice.

It is hoped this get-tough approach will slash nitrogen dioxide levels in the city centre, which in some streets are more than double the Government's air quality standard of 40mg per cubic metre.

But last night, the news was branded "unreasonable" by city cabbies.

Alan Woodward, secretary of the Oxford Licenced Taxi Cab Association, said: "Cab drivers in their 60s and 70s can't sit in a cab in sub-zero temperatures without any heating on and we're not allowed to leave ours cabs unattended.

"We are all for reducing emissions and, with the price of fuel these days nobody wants to sit with their engine on, but we will fight any fine that seems unreasonable.

"I'm severely disappointed the council has decided to push this through without consulting the people affected.

"It would be nice if one of the councillors who makes these decisions would come and sit in a taxi for half an hour without the heating on - I bet they wouldn't sit in Town Hall with no heating."

The Oxford Mail understands a one-minute idling time limit is being looked at as a rough guideline for enforcement.

Those caught in Oxford's traffic jams will not be fined.

Oxford buses already switch off their engines if they expect to wait longer than 60 seconds.

The crackdown will be policed by the city council's two current enforcement officers who already patrol the streets in search of people who litter.

However, environmental health bosses eventually want more manpower to deal with the city's burgeoning pollution problem.

Public health officer Ian Wright said: "Oxford City Council is committed to improving air quality in Oxford.

"The regulations apply to the whole of the city, but the city centre is the priority area. The main aim isn't to fine people or for income generation, it's about improving the air.

"We would like more resources to carry this out, but it's a question of where the money is going to come from.

"A minute time period is one of the things that will be taken into account along with a range of other factors, we don't want to ask people to switch their engine off and on when it is worse for the environment."