Although moves to cut some dangerous pollutants are on track, car emissions are remaining stubbornly around the same level.

The latest effort to improve the UK's air quality is being promoted as the numbers of children falling ill because of the poor atmosphere continues to rise.

Environment Correspondent Richard Wilson: Pollution is a growing concern

Ministers intend to concentrate on improving the situation for the one in five young children now being diagnosed with asthma.

The overall aim of the National Air Quality Strategy is cut pollutants from industry, power stations and road traffic.

Under this latest review some targets will be toughened and others relaxed - but more stringent measures to curb the growing numbers of cars on the road appear inevitable.

Michael Meacher: "We have cross European agreement to cut particles"

Environment Minister Michael Meacher said the government was bringing forward the date to 2003 to reach tougher targets on four of eight key pollutants in the atmosphere.

In the case of particulates, microscopic particles of soot which emitted from car exhausts, the government was taking a lead in Europe in reducing their emission.

Health minister Tessa Jowell will join with Deputy Prime Minister John Prescott to unveil the review.

Plans to cut traffic form part of the strategy

They are keen to stem the rising tide of asthma cases among under-fives, where numbers have almost doubled from 12% to 21% in the last eight years.

The goal of reducing the incidence of asthma was given added urgency by a report last year which linked deaths due to respiratory problems with traffic fumes.

Environment Correspondent Robert Pigott: The level of particles is staying obstinately high

Mr Prescott's integrated transport policy aims to encourage travel by bus, train, cycle and on foot while cutting journeys by private car.

New workplace parking charges and tolls in some areas are part of the plan, but environmentalists warn that it will not be easy meeting air quality targets.

Mr Meacher listed the government's strategy for reducing pollution on BBC Radio 4's Today programme.

He said: "The opportunities for congestion and parking charges will be certainly part of early legislation.

"There are already strong fiscal incentives, ultra low sulphur diesel now ha a 2p deferential compared to standard diesel, that will be 3p in the next budget.

"The duty as the National Society for Clean Air was saying on cheaper and cleaner fuels like liquid petroleum gas and compressed natural gas is lower than standard diesel."