The defeat of the motion by 285-272 votes yesterday after seven hours of impassioned debate in the House of Commons was a setback for Cameron in his bid for a "strong humanitarian response" to the alleged use of chemical weapons by Syria.
Syrian opposition and the West have accused President Assad of using chemical weapons last week in a Damascus suburb killing hundreds of people, a charge denied by the government.
After the stunning defeat, Cameron told lawmakers: "It is clear to me that the British parliament, reflecting the views of the British people, does not want to see British military action. I get that, and the government will act accordingly."
Later, a spokesman for Cameron's Downing Street office said, "Britain will not be involved in any military action".
The defeat of motion raises the prospects that the US could act alone against Syria.
Labour leader Ed Miliband said the result meant military action was "off the agenda", and that MPs had reacted against the prime minister's "cavalier and reckless" leadership.
"I think today the House of Commons spoke for the British people who said they did not want a rush to war," he said.
Miliband said US-UK ties "cannot simply be about doing what the American president says he wants you to do".
In the House of Lords, NRI industrialist and Labour peer Lord Swraj Paul opposed any military strike in Syria, saying "To jump into this turmoil seems at the very least to be lacking in wisdom and failing to recall the recent lessons of both Iraq and Afghanistan."
Lord Paul said the tragic situation in Syria deserves the most extreme condemnation from all nations.
"But I am saddened by the willingness of certain groups in this country, in the United States and Europe to advocate military action in order to punish whoever, in their view, is responsible for recent transgressions," he said.
He said, "for those who have the military power to intervene in others' disputes at their own discretion is a notion that could have potentially dangerous consequences, especially in regions like South Asia."
He suggested the government to "practice restraint and beware of becoming an instrument of the confrontational arrogance of others."