Mr Coleman criticised those who took part in the "orgy of sport"
Britain's Olympic champions are poor role models who are "tainted with blood" over China's human rights record, a London Assembly member said.
Conservative Brian Coleman criticised the winning athletes in a column for newspaper North London Today.
"If you are looking for young heroes and role models, forget the highly paid athletes who leave their consciences at passport control," he wrote.
London Assembly Conservatives said Mr Coleman was entitled to his own views.
Mr Coleman, who also chairs the London Fire and Emergency Planning Authority, criticised athletes for taking part in the "two-week orgy of sport".
"While Britain's athletes may have won more medals than usual they must remember that they are tainted with the blood of Tibetans, Falun Gong practitioners, and Roman Catholic priests who are being tortured and held in labour camps just a few miles from the glittering 'Bird's Nest stadium,'" he wrote.
Mr Coleman added that "our soldiers in Afghanistan and Iraq" were more worthy of admiration than Britain's Olympic medallists.
Britain won 19 golds among 47 medals in Beijing, the best Olympic haul for a century.
On Sunday London Mayor Boris Johnson received the Olympic flag at the closing ceremony, as London prepares to host the event in 2012.
Team GB won 19 gold medals
Labour London Assembly member Valerie Shawcross said Mr Coleman's comments were a "gross insult".
"Mr Coleman has gone out of his way to personally attack, insult and disparage the remarkable achievements of the British team," she said.
"We should be giving our young athletes all the resources and support possible, not rubbishing and going out of our way to put them down."
Mike Tuffrey, leader of the Liberal Democrats group at the London Assembly, said we should be proud of Britain's Olympic athletes, "medal winners or not".
"These athletes are not wealthy premiership footballers but committed and talented sportsmen, who often fit their training around a full time job," Mr Tuffrey added.
"There are of course concerns over China's human rights record but the way to combat this is not by denigrating our athletes."
A spokesman for the mayor said Mr Coleman was entitled to his opinion, but that Mr Johnson did not share the view that the Olympic athletes were "tainted".
"It is offensive to suggest so when these fine young men and women are not only doing Britain proud, but are helping to open China to the world, and the world to China," the mayor's spokesman said.
Mr Coleman declined to comment further.