Cheshire East air pollution report anomalies 'unlikely' to be human error
Environmentalists are demanding to know why a council sent incorrect air pollution data to the government.
Auditors believe the number and nature of the inaccuracies means human error is "unlikely" to have been responsible.
"It's in nobody's interest to be kept in the dark about the true scale" of pollution, Friends of the Earth said.
Cheshire East Council said it would not comment while an investigation establishes "the reason for the errors and who is responsible".
Jenny Bates from Friends of the Earth said the public must be given accurate information about air quality and health problems caused by pollution.
All UK local authorities are obliged to monitor local air quality and submit their findings to the Department for Environment, Food and Rural Affairs (Defra).
According to a council email sent to Defra which has been seen by the BBC following a request under the Freedom of Information Act, issues were found in data submitted by the local authority between 2013 and 2015 "and possibly earlier".
Another council email to the department reveals the "nature and extent" of the anomalies means that "on the balance of probabilities it is unlikely that they are random or the result of human error".
An internal review by council auditors in 2016 found data submitted was different to the original data provided by the laboratory that analysed readings from the council's monitoring equipment.
The council's auditors found effective "air quality management policies (and) procedures" were not in place, and recommended an external investigation.
That investigation is said to be "ongoing".