Prime Minister Theresa May is set to face British lawmakers to explain her decision to launch airstrikes against Syria without a vote in Parliament.
Britain, the United States and France hit targets in Syria on Saturday in response to a reported chemical attack in Douma.
Parliament returns on Monday after a spring break, and was not consulted about the action. The government is not legally bound to seek Parliament's approval for military strikes, though it is customary to do so.
May plans to tell lawmakers that the airstrikes were "in Britain's national interest", were carried out to stop further suffering from chemical weapons attacks and had broad international support.
The government says it will seek an emergency parliamentary debate on the airstrikes on Monday, though that is unlikely to satisfy angry opposition lawmakers.