Ken Livingstone has compared events in China's Tiananmen Square to the history of protest in London's Trafalgar Square during a visit to Beijing.
The mayor visited Beijing's Tiananmen Square
China's human rights record was raised as he went to the site of the 1989 massacre. London's Mayor said his city also had an "interesting history".
He is in the 2008 Olympic Games host city to build trade and tourism links.
But some human rights campaigners said to compare the poll tax riots to the killings was an "insult" to the dead.
Tibet campaigner Yael Weisz-Rind said: "I feel it is really unfortunate to make this comparison. The political and the cultural background and context are not similar."
Estimates of the number of people killed when troops and tanks broke up demonstrations in and around Beijing's Tiananmen Square vary.
The Central Intelligence Agency says 400-800 died, the Chinese Red Cross 2,600. Student protesters say more than 7,000 died.
No one died in London's poll tax riots and the police did not use tanks.
They came after a peaceful march by 70,000 protesters. There were 400 arrests and injuries to 113 people, including 45 police.
Mr Livingstone told reporters: "In the same way that Trafalgar Square has had an interesting history, not always a peaceful one, there's a very clear parallel.
"We've had some interesting riots in Trafalgar Square - I mean, only 20 years ago, the poll tax riots, and flames licking up."
Mr Livingstone said: "If you go back to some of the early instances you will find many cases where innocent protesters were hacked to pieces with sabres - the Peterloo Massacre, for example.
"There is no such thing as one country with a perfect record."
In the 1819 Peterloo Massacre in Manchester, 11 people were killed and 400 injured when local militia waded into a crowd of radicals campaigning for universal suffrage.
Mr Livingstone also met the mayor of Beijing on Monday as part of his visit to promote trade and tourism between the two cities.
He said he hoped to learn and build on Beijing's experience hosting the 2008 Olympics for London's 2012 planning.
Poll tax riots took place in 1990
Mr Livingstone said: "The best way to carry human rights forward is to engage between nations and bring down barriers.
"The more Chinese people that come and visit London, the more Londoners that come here, the better the trade links are and the more we will find that China evolves to the place we would like it to be."
Lord Coe, who led Britain's 2012 Olympic Games bid, is among 70 delegates travelling with the mayor.
They will meet organisers of the 2008 Beijing Olympics to foster relations with the 2012 committee.