An influential group of MPs scrutinising the work of Vosa have been told it is inappropriate that the enforcement agency and the Traffic Commissioners share the same premises.
In a written submission to a Transport Select Committee inquiry, Transport for London also said it was "unhelpful" that Vosa was being used as the secretariat for the TCs.
"The quality and amount of support to the Traffic Commissioners and to the Senior Traffic Commissioner is also insufficient for them to fulfil their roles effectively," it added.
"It should not be for Vosa to decide on these issues, nor is it appropriate for Traffic Commissioners to be in the same premises as Vosa, as this greatly diminishes the appearance of independence so essential for those regulated to have confidence in the regulators they pay for through licence fees."
TfL said the secretariat should be independent of Vosa, echoing the relationship between the police and the Crown Prosecution Service.
Among other issues the inquiry is looking at how the agency can better support the Traffic Commissioners.
A Vosa spokesman explained that there are three sites where the TCs and their support staff share the same building: the Central Licensing Office in Leeds, Jubilee House in Bristol and Golbourne (Warrington).
"The premises are shared as a means of providing accommodation for the Commissioners at an economic cost to the public purse and to reduce the estates footprint of government generally. The cost of space in a large building is generally much less than if the accommodation was in separate, smaller premises," he said.
"In addition, there are clear boundaries between Vosa and the TCs' support staff. Vosa managers do not have any authority to instruct these staff in their administrative function. The role each member of the TCs' support teams is delegated to them by the Commissioners themselves and can be varied/removed at any time."
