Health and safety officials are investigating whether unlicensed workmen employed by the council left the public exposed to deadly asbestos after the substance was found in Fulham Library.
The alarm was raised by library staff after the material, which can cause cancer, was discovered behind a radiator during modernisation works of the ground floor while the library remained open.
It is being alleged that unlicensed workmen then carried the substance through the library's public area, before dumping the toxic waste in the back garden.
The London Hazards Centre (LHS), which has passed on the complaint to the Health and Safety Executive (HSE), says staff came to them after being fobbed off by library management, who insisted the material wasn't dangerous. The matter is currently being investigated by the HSE's prosecutions team.
Margaret Sharkey, from the LHS, accused the council of trying to cover up the discovery. She said: "Local authorities have a duty to ensure the safety of the public and their staff are prioritised. The matter would never have came to light that the council were using unlicensed contractors to remove asbestos and dumping the waste unless we had been informed.
"This is not the first time that public authorities have faced these allegations and the matter of asbestos in public buildings such as schools and libraries is now high on the agenda to ensure we reduce the deaths caused by asbestos-related diseases."
The council says the matter has 'been blown out of all proportion' and denies using unlicensed contractors to remove the asbestos. Councillor Greg Smith, cabinet member for residents' services, said: "This incident has been blown out of all proportion. As soon as the asbestos was found in the library, an expert asbestos disposal company was called to the scene which disposed of it in a safe and appropriate manner. The library was immediately tested and no traces of harmful asbestos dust was found.
"No members of the public were in the vicinity and there is absolutely no health risk to anyone at the building at the time or anyone who may have visited since. The asbestos was safely removed to a secure site at the back of the library building and has now been disposed of off-site."