The warning came after London Mayor Ken Livingstone on Monday launched a £500M plan to build a network of up to 12 unbroken cycle lanes on key radial routes into London.
The network will take up significantly more road space than current cycle lanes and would see road junctions redesigned.
"I think we have to be concerned about reserving more road space on the back of some idealistic idea of increasing cycling by 400%," said Freight Transport Association external affairs director Geoff Dossetter.
"There is a terrible risk of dedicating valuable road space to something that is underused while other traffic gets more congested."
A Transport for London spokesman said that the loss of road space to cars and HGVs would be compensated for by fewer cars on the road as people switched from cars to bicycles.
TfL is understood to be considering routes into central London from Hackney, Clapham, Kilburn and Ealing.
The first would be delivered by 2010 followed by five more in time for the 2012 Olympics. The aim is to increase cycling in the capital by 400%.
"We want to create wider lanes that are very heavily signposted," said the TfL spokesman. "It will be made much clearer that it is a facility for cyclists so we would get a critical mass of people using it." The scheme will also create 20pmh "bike zones" in 15 suburban town centres in an attempt to make streets safer for cyclists.