Speaking on BBC Breakfast Shadow foreign secretary Douglas Alexander said:
The right response is not simply to say something must be done, however loudly. It is to both ask and answer the question 'What steps can be taken to make a horrendous situation better?'
Now, as the Labour Party, we have never in principle ruled out the use of force in Syria. But we haven't yet heard from the Government what its strategic objective would be for any military action.
Would it be to degrade and diminish the capability of Assad to use chemical weapons? Would it be an attempt to try and change the course of a highly complex, intractable civil war?
We simply haven't had those questions answered.
And that's why I do think the Prime Minister should bring Parliament back so that they can offer their case both to politicians and to the people before any decision is taken to commit British forces into combat.
The Prime Minister has said 'the world should not stand idly by' after hundreds were killed in apparent chemical attacks in Syria last week.
Any UK military action in Syria would involve submarine-launched cruise missiles rather than air strikes, a military expert has predicted.