Ministers face questions over the UK's military action against Islamic State (IS) after it emerged RAF fighter jets have been concentrating on targets in Iraq, despite being given the go-ahead by Parliament to bomb the extremists in their Syrian heartlands.
Foreign Secretary Philip Hammond is certain to be grilled on the issue when he gives Parliament a promised update on the mission.
In the marathon Commons debate on December 2 that ended with MPs voting to approve strikes in Syria, David Cameron said that it was important to hit IS in its capital, Raqqa - the "head of the snake" - from where it plotted its terror attacks on the West.
However the latest update from the Ministry of Defence revealed that British warplanes have not hit IS - also referred to as Daesh, Isis or Isil - in Syria since December 6.
Since then the Tornado GR4s and Typhoon FGR4s stationed at RAF Akrotiri - backed by unmanned Reaper drones - have only struck in Iraq where they are supporting Kurdish ground forces attacking IS.
The disclosure is likely to fuel criticisms there are few targets left to hit in Syria after months of US air strikes and that the Government's decision to extend British strikes from Iraq into Syria was largely symbolic.
The potential implications for the UK of a new Saudi Arabia-coordinated military alliance of mostly-Muslim countries against extremists are also set to be discussed by MPs.
Riyadh did not rule out the 34-nation grouping deploying ground troops to conflicts such as Syria - which the Telegraph said could require British military support.
But the failure to include Shia Muslim-run states such as Iran and Iraq - or Syria itself - in the alliance raised questions about how it could intervene effectively and who its targets would be in the absence of full details.