The figures, from the Government's pollution database, show sharp increases in the number of days when the air in Britain's cities was seriously polluted by particulates, tiny particles emitted by burning fuel, which are estimated to kill 10,000 people each year - particularly through strokes and heart and lung disease.
The figures - dug out of the database by Friends of Earth, which has special access to it, and still to be completely validated - show that the number of days when the pollution exceeded the Government's planned safety limit rose in all but three of the 15 official monitoring sites.
In Leeds they rose by 18 per cent over the 1995 figure to 45 days, in central London by 20 per cent to 55, in Bristol by 30 per cent to 35, in Hull by 40 per cent also to 35, and in central Birmingham by 50 per cent to 34 days. The worst affected city is Belfast, which saw a trebling of serious polluted days from 40 to 124.
The Government will have a much harder job to get the pollution under control that had been predicted. It is aiming to eliminate the number of days exceeding the safety limit by 2005 - but this objective was based on the relatively clean conditions of previous years and much more rigorous measures may now prove to be necessary.
Germany and Austria are trying to persuade the EU to cut the amount of sulphur in diesel by a tenth by the year 2000, which would sharply reduce the pollution, but Britain is insisting on a much more modest reduction.
Roger Higman, Senior Transport Campaigner at Friends of the Earth said yesterday: "These figures prove that the problem is not going away. Urgent measures are needed to cut the emissions. Cleaner, low sulphur diesel can bring emission levels down quickly at a cost of less than pounds 10 a year per car. The Government must make its use mandatory."