Making Oxford city centre a Low Emission Zone (LEZ) in a bid to cut pollution levels has not worked, according to campaigners.

In April, the city council declared one of the country’s first LEZs to tackle air quality which had fallen below EU standards for nitrogen dioxide pollution.

The zone means that by 2014 only buses and coaches which meet strict European standards will be able to operate in central Oxford.

But six months after its introduction, the scheme has been criticised for failing to ban all polluting vehicles, such as taxis, vans, and lorries.

Carfax councillor Sushila Dhall said: “I think it’s shocking the LEZ is so toothless and ineffective. The zone has had no impact on reducing pollution whatsoever.

“With pollution we’re talking about an on-going threat to people’s health who live, work, study or shop in the city.

“When the LEZ was declared there was a huge splash of publicity but I have always thought it was a missed opportunity.

“No-one’s putting any pressure on any other car or van drivers to make them cleaner.”

Ms Dhall, who cycles through the city centre to work every day, added: “I regularly have to hold my breath going through queues of traffic in the city centre because the fumes are so bad.”

Two months ago it emerged St Aldate’s was the ninth most polluted street in England for nitrogen levels.

The council has defended the LEZ, arguing that it would be too difficult to enforce a ban on all ‘dirty’ vehicles and that buses and coaches are responsible for 80 per cent of pollution.

City councillor John Tanner, board member for a Cleaner, Greener Oxford, said: “The bus companies are already bringing into service low emission vehicles which are improving air quality not only in the city centre but in the rest of Oxford.

“The LEZ and the discussions we and the county are having with those companies will see those vehicles brought into service sooner.

“In the city centre 80 per cent of pollution is caused by buses so why use time and money kicking the odd lorry or car when we are already delivering the solution.

“We could insist on the low emission vehicles tomorrow, but this would put up fares and probably makes the bus companies bankrupt.”

Paul Cullen, the chairman of Oxford Pedestrians Association, said: “I’m very disappointed in the LEZ.

“This is about more than just about pollution from buses.

“It should apply to all vehicles standing still in traffic jams, such as those in Hythe Bridge Street and Beaumont Street where the pollution is pretty appalling and you hardly ever see a bus.”

Oxford Bus Company operations director Louisa Weeks said: “We will meet the council’s target by 2014, but the main frustration is the LEZ will not include goods vehicles, taxis and other vehicles.”