A bus lane on Coulsdon's new multi-million pound relief road is going largely unused because no public transport uses the bypass.
Transport for London (TFL) confirmed local buses use the A23, which runs through Coulsdon town centre, instead of the new relief road.
However, a TFL spokesman said the lane was a priority route for coaches, taxis, motorcycles and HGVs weighing more than three and a half tonnes.
Critics said the lane is pointless, confusing and exacerbates congestion.
Peter Morgan, from the Croydon Road User Forum, said: "It is very peculiar. You see bus lane' written in big letters but no buses go down there. HGVs and other vehicles are allowed to use it but I think it's confusing for motorists. Congestion is bad on the bypass and we could do with that lane being free to ease traffic."
John Jackson, from the Anerley Bicycle Club, said: "In their wisdom the authorities paint bus lane' on the road and then designate it a HGV lane to confuse everybody and pocket any fines.
"Just the kind of muddled thinking we have come to expect from traffic engineers - and a cover-up of an expensive cock up. Or was it?"
The long-awaited Coulsdon relief road opened last December to queues of traffic, angering motorists who were expecting congestion-free journeys.
Andrew Pelling, London Assembly member for Croydon and Sutton and Conservative MP for Croydon Central, said: "It is utterly ridiculous to have a bus lane with no buses. I'm afraid this is Ken Livingstone at his politically-correct best. If we want road space used sensibly then we will have to wait until a different mayor is elected."
Richard Ottaway, Conservative MP for Croydon South, said: "The original plans did not have a bus lane but Ken Livingstone did not want to be seen to be building a dual carriageway.
"We should not lose sight of the purpose of the bypass, which was to take pressure off Coulsdon town centre. I didn't support the bypass to help someone from Sussex drive up to London more quickly."
A TfL spokesman said: "Although all local buses run through the centre of town there are other buses, including school buses, mini buses, coaches and long distance scheduled services, which can and do use the priority lane.
"The lane also provides priority for goods vehicles, which are essential to London's economy, motorcycles, which make better use of road space than private cars, and taxis which are a form of public transport, with minimal disadvantage to general traffic."
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