A crash during Sunday's final stage of the Tour of Britain has led to growing concerns about London's ability to host two stages of the 2007 Tour de France.
Five people were injured after a police motorcyclist collided with a marshal's motorbike on The Mall.
The peloton had already made a go-slow protest on Saturday over concerns that roads were not being securely blocked.
The organisers of the British event, Sweet Spot, are also expected to be involved in the 2007 Tour next July.
Cyclists complained during stage three of the Tour of Britain in Sheffield that rolling roadblocks were still allowing traffic to seep through.
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The same complaints were made in London and the crash, in which the motorbikes ploughed into crowd barriers, further highlighted the need to tighten safety procedures.
All roads along the route will be closed completely for the Tour de France and, with 3m spectators expected to line the streets, safety will be a priority.
The cyclists made their feelings clear with a protest in the penultimate stage through Kent from Rochester to Canterbury.
World champion Tom Boonen said: "All the circumstances were there for someone to get injured."
"British cycling has a lot to be proud of and they have shown no respect to the Tour"
The views of some senior European professional riders, such as Boonen, is a further blow to British cycling.
This conflict of opinion between the Europeans and the domestic racers has also provided another sour footnote to the Tour of Britain
Kent's Kristian House, was pushed into a gutter by senior riders determined to aggressively set the pace.
Fellow Briton Ed Clancy, who rides for Belgian team Landbouwkrediet, was critical of his European counterparts.
"It's 100% unacceptable," said Clancy. "They just couldn't be bothered to race.
"British cycling has a lot to be proud of and they have shown no respect to the Tour."
The opening stage of the Tour de France takes place in London in Trafalgar Square on 7 July with the prologue time trial and a stage from London to Canterbury following over the next two days.