Theresa May is to face MPs' questions about her decision to authorize air strikes against the Syrian government. Opposition parties say MPs should have been consulted before the UK joined the US and France in bombing three Syrian sites, in response to a suspected chemical attack on the town of Douma. Labour has called for the law to be changed for any future interventions.
Foreign Secretary Boris Johnson promised MPs would have abundant time to have their say.
Sites near Damascus and Homs were hit on Saturday in response to the alleged chemical attack on Douma on 7 April. Both Syria, which denies any chemical use, and Russia, which provides military support to the Syrian government, have reacted angrily to the action.
UK prime ministers do not legally need to consult Parliament before launching military action, although they have done so since the 2003 invasion of Iraq.
Mrs May is due to give a Commons statement this Monday before facing questions from MPs. She is also expected to ask the Speaker for permission to hold an emergency debate in Parliament on the issue of Syria.
Her decision to authorize action without MPs' backing has been criticized by Labour leader Jeremy Corbyn, who said she could easily have recalled Parliament or delayed her decision until MPs returned to Westminster from the Easter recess.
Mr Corbyn called for a new War Powers Act so governments do get held accountable to Parliament for what they do in our name. This was dismissed by cabinet minister David Lidington, who told ITV there were no plans to change the law.
Governments have to bear in mind the need to be able to act swiftly and flexibly and to protect the safety of our servicemen and women, he added.
The Scottish National Party said it would table a motion for an emergency debate to try to get MPs a vote on whether they backed the action.
Mr Corbyn, who has warned of an escalation in a proxy war between the US and Russia, said he would only consider backing intervention in Syria with the support of the United Nations.
If we could get to a process in the UN where you get to a ceasefire, you get to a political solution, you then may well get to a situation where there could be a UN force established to enforce that ceasefire, he told the BBC's Andrew Marr Show on Sunday. That surely would save a lot of lives.
But the Conservatives said he knew full well that Russia would veto such a move.
Downing Street published its legal case for its parts in the strikes, stating that the action was legally justified on humanitarian grounds.
On Saturday, the UK Ministry of Defense said eight Storm Shadow missiles had been launched by four RAF Tornados at a former missile base, 15 miles west of Homs. It is thought President Bashar al-Assad's regime had been stockpiling materials used to make chemical weapons there, it said.
The MoD added the facility was located some distance from concentrations of civilian habitation, and the risk of contamination to the surrounding area had been minimized.
On Saturday, the UN Security Council rejected a resolution drafted by Russia, while all Nato allies have given the military action their full support. There has been no confirmation of any civilian casualties.