The report, by a senior scientist at Sussex University, estimates that the intelligence of one in every 10 children under six has been diminished by exposure to the toxic metal at a time when their brains are developing. That would mean over 440,000 of them had been affected.
The report says that government departments have been "negligent" and "culpable" in doing little to tackle the two main causes of this exposure, lead in paint and drinking water.
The Government has no programme for dealing with leaded paint and water companies do not have to bring levels of the poison in drinking water down to official World Health Organisation (WHO) limits until at least the year 2010.
The findings, by Dr Erik Millstone, Senior Lecturer at the university's prestigious Science Policy Research Unit, will come as a shock because the gradual phasing out of lead from petrol has been one of the environmentalists' greatest achievements. It demonstrates that a widespread danger remains from sources largely ignored by green campaigners and government departments alike.
Publication of the report also coincides with a mass water rates strike by villagers in mid-Wales, who are refusing to pay because they believe their water supply to be contaminated. Householders in Libanus, Powys, say laboratory tests revealed excessive levels of lead, iron and manganese.
No one knows exactly how many children are affected because Britain, unlike the US, does not carry out systematic monitoring to determine the size of the problem. But, using evidence from Britain and the US, Dr Millstone calculates that 10 per cent of children have more than 10 micrograms of lead per litre of blood, the level at which measurable effects on IQ have been detected. There seems to be no safe level.
The Government admits its own limited research has found that five per cent of toddlers have these levels in their blood. Even if this lower figure is right, about a quarter of a million children would still be affected.
The report says: "Children are being poisoned mainly because of the presence of old leaded paint with which their homes were decorated in years gone by and because their water supply is reaching them through old and totally outdated water pipes."
It says some 10 million homes receive drinking water through lead piping, either within the house or in the water company's system, or both. Among areas worst affected are south-west Scotland and Lancashire. Acidic water dissolves toxic metal in the pipes, but the last government cut grants to enable households to replace them. It also failed to honour a promise to ban the use of lead solder in domestic pipes.
Britain allows 50 micrograms of lead per litre of water, five times the level recommended by the WHO. A European directive, expected to be adopted next year, will force water companies to cut this to the WHO level when it enters houses, but this need not be implemented until at least 2010. Britain also has no official target for levels of lead in children's blood.
n A report to be launched at TUC headquarters on Tuesday will reveal that children who spend too much time at the computer are at risk of being crippled by repetitive strain injury. Research carried out by the Body Action Campaign blames a lack of suitable equipment and training at home and at school.Reuse content