Russia and China vetoed a UN Security Council resolution Saturday that backed an Arab League plan calling on Syrian President Bashar Assad to step down.
The remaining 13 council members, including France, the U.S. and Britain, voted in favour.
Western and Arab nations had been pushing hard for a strong resolution that demanded Assad hand power to his vice-president.
Canada's Foreign Affairs Minister John Baird said in a release Saturday the failure of the UN vote is another "free pass for the illegitimate Assad regime and those backing it."
He said Canada continues to support the efforts of Syria's neighbours and others to resolve the crisis.
"Those attempting to cling to power in Syria are morally bankrupt, and their disregard for human life is surpassed only by their cynicism for doing what is just and right," Baird said.
The vote came on the same day Syrian activists said more than 200 people were killed in the city of Homs after security forces fired mortars and artillery rounds overnight.
After the vote, U.S. Ambassador Susan Rice said the United States was "disgusted" by the vetoes. She accused Russia and China of aiming to "sell out the Syrian people and shield a craven tyrant.
"For months this council has been held hostage by a couple of members," Rice said. "These members stand behind empty arguments and individual interests while delaying and seeking to strip bare any text that would pressure Assad to change his actions.
"Any further bloodshed that flows will be on their hands," she added.
"It's a sad day for this council, a sad day for Syrians and a sad day for all friends of democracy," said French ambassador Gerard Araud after the vote.
Russia and China "made themselves complicit in a policy of repression carried out by the Assad regime," he said.
The German ambassador was equally disgusted with the outcome of the vote.
"Today the Security Council has failed to live up to its responsibility. The people in Syria have been let down again," said Peter Wittig.
Russia has steadfastly supported the Syrian government - its only remaining ally in the Middle East - during the conflict and has refused to stop shipping weapons there.
Russian Foreign Minister Sergey Lavrov said earlier Saturday the resolution didn't go far enough dealing with armed anti-Assad groups, he said.
Russia is also attempting to get political forces inside Syria to negotiate an end to the violence and didn't want a resolution to prejudge the outcome.
While the U.S. and its allies have ruled out military action, it wanted the Security Council to endorse the Arab League plan.
Protests also broke out around the globe Saturday as at least five Syrian embassies were stormed in Europe and the Middle East in response to the alleged massacre in Homs.
Police in London beat back protesters attempting to get into the Syrian embassy after succeeding earlier in the day, managing to break a few windows.
The embassy in Athens was also broken into before dawn and 13 people detained. Offices at the embassy in Berlin were also entered and damaged, officials say.
More than 5,400 people have been killed in the uprising since March, the UN reported in December, but it hasn't been able to update those numbers in recent weeks due to the chaos in the country.
-with files from The Associated Press
