The small Northern Irish political party that props up her government said May was justified in taking such action.
The leader of Britain's largest opposition party is suggesting Theresa May, the prime minister, could face a backlash in parliament for her decision to join the USA and France in launching strikes against Syria.
"The consequences of any country taking unilateral and action that has no legal basis are that it's an encouragement for others to do exactly the same and reduces our ability to complain when others do that", he said.
Corbyn also asked for the legal advice given to the Attorney General regarding the attack to be published, and called for Britain to work towards a ceasefire.
In Britain, opposition is building up to any British involvement in military strikes in Syria, particularly without the issue being taken to Parliament first.
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"The Government should do whatever possible to push Russian Federation and the United States to agree to an independent UN-led investigation of last weekend's horrific chemical weapons attack so that those responsible can be held to account".
The Labour leader's condemnation came as the SNP's Nicola Sturgeon warned that the airstrikes could make the seven-year civil war in Syria worse, and accused Ms May of "complying with Presidential wishes".
"Riding the coattails of an erratic US President is no substitute for a mandate from the House of Commons", he said.
He added: 'Theresa May should have sought parliamentary approval, not trailed after Donald Trump.
Often when the British government decides on military action, the opposition offers its full support.
In a summary of the advice given by Attorney General Jeremy Wright to Prime Minister Theresa May, Downing Street pointed the finger at Moscow over its role in leading the United Kingdom and its allies to decide to launch an attack on Bashar Assad's regime.
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Diplomatic action, sanctions, and the USA strikes against the Shayrat airbase in April 2017 have failed to sufficiently degrade Syria's chemical weapons capability, the document added.
"Airstrikes have not resolved [the] situation in Syria so far - nothing I've heard persuades me they will do so now".
She added: "This action risks not just further escalating the civil war in Syria but also a risky escalation of worldwide tensions".
"UK foreign policy should be set by Parliament, not US President".
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