Air pollution on a road which is temporarily closed "to improve air quality" has never been monitored, a council has admitted.
Boots Corner, in Cheltenham, has been closed to private vehicles since June as part of the town's transport plan.
A meeting was told an air pollution monitor had not been installed despite the scheme being approved in 2015.
Cheltenham Borough Council said the monitoring is done in accordance with the Defra guidance.
The town is one of 33 areas in England with levels of air pollution that breach European Union targets.
The council had to write to the government's environment department earlier this year detailing how it would crackdown on the issue",
According to the borough council's website, it states the transport plan aims to "put people and spaces first by improving air quality".
But councillor John Payne questioned the approach the council had taken to assess the air quality of Boots Corner.
Mr Payne said: "According to the map, there is no air pollution monitoring in Boots Corner.
"They're not monitoring of particulates in the study, and that is a serious omission," he added.
Speaking after the meeting a council spokeswoman told the Local Democracy Reporting Service a monitor had not been fitted to Boots Corner "because it isn't a residential area".
She said the authority is not required by government to monitor where there are no "relevant public exposures," namely residential properties.
"It's important to note that air quality improves in general when there is less traffic," she added.