Don't try and pretend to me it's in our national interest.
Mrs May said chemical weapons had all too often been used in recent times.
Asked whether he would back a vote at the end of Monday's debate, opposition Labour leader Jeremy Corbyn told the BBC: "Yes I would, because I think parliament should have a say in this and the prime minister could quite easily have done that".
"Bombs won't save lives or bring about peace", he said in a statement. Macron said in an interview broadcast by BFM TV, RMC radio and Mediapart online news that he had convinced Trump to focus on the chemical weapons sites.
A YouGov poll of 1,600 British people, published on Thursday, found that only 22% supported military action against Syria, while 43% opposed it.
"This was not about interfering in a civil war, and it was not about regime change", May said on Saturday.
"We are prepared to sustain this response until the Syrian regime stops its use of prohibited chemical agents".
Stewart McDonald of the Scottish National Party said: "The PM has engaged United Kingdom forces in gesture bombing, with no major global consensus and no long term plan to halt the use of chemical weapons or deliver peace".
The chairman of the worldwide affairs committee of Russia's upper house of parliament, Konstantin Kosachev, said the strikes were a violation of worldwide law and probably created to prevent investigators from the global chemical weapons watchdog from doing their work.
The action was highly targeted, necessary and proportionate to alleviate humanitarian distress and therefore legally justifiable it added.
The Labour leader added that weapons inspectors were on their way to verify the use of chemical weapons by the Assad regime.
The targets included a Syrian center in the greater Damascus area for the research, development, production, and testing of chemical and biological weaponry as well as a chemical weapons storage facility near the city of Homs.
Russian agencies quoted the lawmakers as saying that Assad was in a "good mood", had praised the Soviet-era air defence systems Syria used to repel the Western attacks and had accepted an invitation to visit Russia at an unspecified time. Indeed, we have been calling for Parliament to be recalled since last Wednesday.
A French frigate, UK Royal Navy submarines laden with cruise missiles and the USS Donald Cook, an American destroyer equipped with Tomahawk land attack missiles, have all moved into range of Syria's sun-bleached coast.
Moscow's ambassador to Washington Anatoly Antonov warned that such actions will not be left without consequences.
The group said it "strongly condemned" the action and accused May of "sanctioning killing" at U.S. President Donald Trump's behest.
State news agency SANA, quoting an official in Syria's foreign ministry, said: The barbaric aggression will not affect in any way the determination and insistence of the Syrian people and their heroic armed forces.