Speaking before the House of Commons, British Prime Minister David Cameron said Paris and London are presenting a resolution to the U.N. Security Council condemning Syria's crackdown on anti-government protesters and demanding humanitarian access in the country.
"There are credible reports of a thousand dead and as many as 10,000 detained and the violence being meted out to peaceful protesters and demonstrators is completely unacceptable. Of course, we must not stand silent in the face of these outrages - and we will not," said Cameron.
France has echoed that tough rhetoric. Foreign Minister Alain Juppe says Syrian President Bashar al-Assad has lost all legitimacy to rule his country.
The new push by London and Paris underscores a more robust collaboration between the two countries who have also led the NATO bombing campaign against the Libyan regime.
Meanwhile in Paris, Syria's ambassador to France, Lamia Shakkour, denied reports carried on international broadcaster France 24 that she had resigned to protest the violence in Syria.
Shakkour told France's BFM TV that France 24 carried "disinformation" and that she would file a lawsuit against the station. France 24 had broadcast a live interview with a woman who identified herself Shakkour and who announced her resignation. In a statement, the television channel said it could not rule out being manipulated or provoked.
Syria also faces international pressure for its alleged nuclear activities, with the United States and other members of the International Atomic Energy Agency pushing to bring Damascus before the U.N. Security Council for non-compliance.