"There is no proof that the Assad regime is responsible for the chemical attack on civilians", Batten said, referring to the Syrian government headed by Syrian President Bashar al-Assad.
The Ministry of Defence (MoD) said that four RAF Tornado jets were deployed to launch missiles at a Syrian military facility.
"This is the first time as prime minister that I have had to take the decision to commit our armed forces in combat - and it is not a decision I have taken lightly", she said.
Although the British government on Saturday defended its decision to join the USA -led military strikes on Syria without consulting Parliament first, British opinion leaders immediately questioned about the Whitehall's legal justification of such a military action.
U.S., British, and French forces launched air strikes against targets in Syria in the first coordinated Western military action against the Damascus regime.
Russia, which intervened in the war in 2015 to back Assad, has denied there was a chemical attack and has accused Britain of helping to stage the Douma incident to stoke anti-Russian hysteria. "No other group could have carried this attack", May said.
"Let these united actions send a clear message to the regime - the use of chemical weapons is categorically unacceptable and you will be held to account".
I have done so because I judge this action to be in Britain's national interest.
Many politicians in Britain, including some in May's own Conservative Party, had called for parliament to be recalled from a break to give authority to any military strike.
Prime Minister Theresa May during a press conference in 10 Downing Street, London on the air strikes against Syria.
Meanwhile, Britain's main opposition Labour leader Jeremy Corbyn described the USA -led military strikes on Syria jointly staged by three leading Western countries as a "legally questionable action", saying that the British government should "not taking instructions from Washington".
"It was right to take the action that we have done in the timing that we have done", she said.
Iranian President Rouhani says US-led military strikes in Syria will cause "destruction" in the Middle East.
Polls in recent days have shown public wariness of military intervention in Syria, with Britain still haunted by its participation in the US-led invasion of Iraq.
"Our service personnel have played an important role in terms of degrading the ability of the Syrian regime to use chemical weapons in the future", Williamson said.