Poll: Should Britain be involved in air strikes against Isis?
David Cameron is facing calls from some Conservative MPs to leave open the option of British air strikes on Islamic State forces in Syria.
As MPs began heading back to Westminster for today's emergency Commons vote on military action against IS in Iraq, senior Tories said that it may not be sufficient to defeat the militants.
Mr Cameron has deliberately restricted Britain's involvement to Iraq in part to secure the support of Labour, which has raised concerns about extending air raids into Syria without specific authorisation of the United Nations Security Council.
Do you think Britain should be involved in air strikes against Isis? Join the debate and leave your comments below.