Housing developers twice failed to tell residents asbestos had been found on a former factory earmarked for new homes, the BBC has learned.
The tests revealed contamination levels 23 times the HSE's limit
Two tests found levels of asbestos 23 and 13 times the Health and Safety Executive's limit, documents revealed.
Developers MMC want to build 650 homes on the site of the former Turner and Newall factory, in Spodden Valley, Rochdale, Greater Manchester.
MMC and its analysts Encia refused to comment on the allegations.
However, MMC confirmed that the report seen by the BBC was legitimate.
The proposed housing development is on the site of what was once one of the world's largest asbestos factories.
MMC's analysts Encia had told residents at a public meeting in May that no asbestos was found in heavy "crush" rubble at the site.
But it failed to reveal that asbestos had been found in soil samples and fine rubble.
It is believed no residents asked specifically about results from the different type of rubble.
A month later, in an e-mail to Rochdale Councillor Tom Stott, MMC also said no asbestos had been found in heavy rubble at the site.
Asbestos was found twice on the site, the BBC has learned
It followed the firm's planning application in December 2004, in which it said there was ''a notable absence of asbestos at the site''.
The Health and Safety Executive's recommended limit for hazardous waste is 0.1%.
The test results showed that two separate samples revealed 1.3% and 2.3% asbestos.
This means the developers need to obtain a special licence in order to clear the asbestos.
Jason Addy, of residents group Save Spodden Valley, said: "Quite simply I suggest this is a wilful omission.
"This could be a heavily contaminated site and the people of Rochdale deserve the truth, the whole truth, and nothing but the truth."