Stewart McDonald, the party’s defence spokesman, has called on the UK Government to work with international partners to clamp down on the suspected use of chemical weapons in the Middle Eastern state, which has been ravaged by years of civil war.
The MP said any change to the role of UK forces in Syria must be subject to a vote in Parliament, and warned air strikes had not prevented the alleged attack in the Syrian town of Douma, a former rebel stronghold in the Eastern Ghouta region.
Theresa May spoke yesterday with Donald Trump and French president Emmanuel Macron regarding the incident, which has been blamed on forces loyal to Syrian president Assad.
Downing Street told the BBC the separate phone calls established the countries would work together to take action to “uphold the worldwide prohibition on the use of chemical weapons”.
Senior UK Government figures have denied Mrs May is hesitating in joining the US and France in launching air strikes against Syrian targets.
MPs do not return to Parliament from Easter recess until April 16.
Mr McDonald said: “The suspected chemical weapons attacks in Syria must be condemned in the strongest terms, and action must be taken to ensure such attacks never happen again.
“The harrowing images of children and adults, killed and injured in these brutal and barbaric attacks, show the need for the UK government to work with our international partners to clamp down on the development and use of chemical weapons in Syria, and hold those responsible to account.
“This must mean action to block the Syrian government’s purchasing and importing abilities, further sanctions against personnel and companies involved, and increased efforts to document those involved in chemical warfare infrastructure to support war crimes prosecutions.
“While the need for action is clear - that action must be properly considered. Air strikes have not prevented these attacks and will not provide the long term solutions needed to end the war. Any proposed change to the role of UK forces in Syria must be subject to full scrutiny and a vote in Parliament.”