London ? It’s billed as the world’s most ambitious attempt to ease traffic gridlock: Starting at 7 a.m. today, motorists will be charged $8 a day to drive into central London, a crowded eight-square-mile area that includes the bustling financial district.

Not surprisingly, the controversial plan — a pet project of Mayor Ken Livingstone — has fierce opponents, though supporters admire its gutsy innovation.

“The system is unique and has not been introduced on this scale anywhere in the world,” declared Stephen Glaister, professor of transport and infrastructure at London’s Imperial College — and also on the board of Transport for London, the body charged with implementing the mayor’s plan.

Livingstone predicts the toll will cut the volume of traffic in the zone by 20 percent, ease congestion and raise $208 million a year for public transport investment.

Then again, he also worries the toll could end his political career. “But what’s the point of being in politics if you don’t do something with your position?” he asked, in an interview with the British Broadcasting Corp.

Opponents say London’s creaking buses and outdated subway system will not be able to handle the strain when thousands of motorists opt for public transport.

Inner city businesses complain the charge will drive up costs, and public sector workers such as nurses and teachers say they should be exempt.

The project is “sadly misguided, incredibly over-elaborate, technically flawed and likely to do no good at all,” said Steve Norris, the Conservative candidate for next year’s London mayoral election. He promised to scrap the toll if he manages to oust Livingstone.

John Biggs, chair of the London Assembly’s transport committee, predicted misery for commuters on London’s Underground.

A driver stops his scooter near a C painted on the road, which marks the start of the London toll for 4-wheel vehicles at the Wellington monument, background, in London. The cameras above the traffic lights, left, will record the vehicles number to determine whether the toll to enter central London has been paid.

“The scheme will be good news for motorists but mean harder times for those who use the already overcrowded public transport system,” he said.

In central London, traffic speed averages just under 10 mph during the day and motorists spend half their driving time stuck in jams, City Hall says.

Livingstone insists that while motorists may not like the charge, they accept that change is necessary.

Drivers can buy daily, weekly, monthly or yearly passes by credit card on the Internet or by phone, or pay by cash or check at post offices and some shops, and must quote their license plate number.

A network of 800 cameras linked to a bank of computers will police the zone, photographing license plates between 7 a.m. and 6:30 p.m. weekdays.

Computers will automatically check plate numbers against a huge national database and those yet to pay will be given until midnight before being fined $65, rising to $130 after two weeks and $200 after 28 days.