Theresa May will face MPs over her decision to launch air strikes against Syria as Labour questioned the legality of the bombing raid.
The Prime Minister is expected to face anger in the Commons after launching military action without securing the support of Parliament.
As well as facing MPs' questions, she will also take the unusual step of calling an urgent debate - although this is expected to fall far short of an explicit vote on the military action demanded by some in the Commons.
Foreign Secretary Boris Johnson insisted the strikes - co-ordinated with action by the United States and France - were "right for the UK and right for the world".
The Prime Minister will say the UK joined the United States and France in co-ordinated strikes following the chemical weapons attack in Douma to "alleviate further humanitarian suffering".
Mr Johnson, speaking at a summit of European Union foreign ministers, stressed it was "not an attempt to change the tide of the war in Syria or to have regime change" and "the Syrian war in many ways will go on in its horrible, miserable way".
"But it was the world saying that we have had enough of the use of chemical weapons, the erosion of that taboo that has been in place for 100 years has gone too far under Bashar Assad," he said.
But shadow attorney general Baroness Chakrabarti questioned the Government's justification for the air strikes, telling BBC Radio 4's Today programme: "You can't use force under international law just to punish Syria for bad behaviour.
"You have to actually be using urgent, necessary and proportionate force. And you have to do it with the will of the world behind you."
She added: "I think that Parliament should have been recalled before the strike. Some people will suspect that that didn't happen because of governmental concerns that they couldn't get the vote in Parliament. And that to me is not a good enough reason."
Labour leader Jeremy Corbyn, writing in The Guardian, said: "The military action at the weekend was legally questionable.
"The Government's own justification, which relies heavily on the strongly contested doctrine of humanitarian intervention, does not even meet its own tests.
"Without UN authority it was again a matter of the US and British governments arrogating to themselves an authority to act unilaterally which they do not possess."