Although the effects on the babies are not clear, the survey prompted several members of US Congress to press for legislation that would strengthen controls on chemicals in the environment.

The report by the Environmental Working Group is based on tests of 10 samples of umbilical cord blood taken by the American Red Cross.

They found an average of 287 contaminants in the blood, including mercury, fire retardants, pesticides and the Teflon chemical PFOA.

"These 10 newborn babies ... were born polluted," said New York Democrat Representative Louise Slaughter.

"If ever we had proof that our nation's pollution laws aren't working, it's reading the list of industrial chemicals in the bodies of babies who have not yet lived outside the womb," Ms Slaughter said.

Cord blood reflects what the mother passes to the baby through the placenta.

"Of the 287 chemicals we detected in umbilical cord blood, we know that 180 cause cancer in humans or animals, 217 are toxic to the brain and nervous system, and 208 cause birth defects or abnormal development in animal tests," the report said.

Blood tests did not show how the chemicals got into the mothers' bodies.

Among the chemicals found in the cord blood were methylmercury, produced by coal-fired power plants and certain industrial processes. People can breathe it in or eat it in seafood and it causes brain and nerve damage.

Also found were polyaromatic hydrocarbons, or PAHs, which are produced by burning petrol and garbage and which may cause cancer; flame-retardant chemicals called polybrominated dibenzodioxins and furans; and pesticides including DDT and chlordane.

The same group analysed the breast milk of mothers across the United States in 2003 and found varying levels of chemicals, including flame retardants known as PBDEs. This latest analysis also found PBDEs in cord blood.

The Environmental Working Group report coincided with a Government Accountability Office report issued yesterday that said the Environmental Protection Agency does not have the powers it needs to fully regulate toxic chemicals.

The GAO, the investigative arm of Congress, found that the EPA's Toxic Substances Control Act gives only "limited assurance" that new chemicals entering the market are safe and that the EPA only rarely assesses chemicals already on the market.

"Today, chemicals are being used to make baby bottles, food packaging and other products that have never been fully evaluated for their health effects on children - and some of these chemicals are turning up in our blood," said New Jersey Democrat Senator Frank Lautenberg, who plans to co-sponsor a bill to require more testing of toxic chemicals.

Pollutants and other chemicals are believed to cause a range of illnesses. But scientists agree the only way to really sort out the effects is to measure how much gets into people and then see what happens to their health.