A senior Labour frontbencher has confirmed to the Huffington Post UK that the Opposition could table an amendment to the government's resolution on Syria on Thursday. Such an amendment would demand that any action against the Syrian regime be UN-led and not begin until after the UN inspectors in Damascus had completed their work.
Even if the amendment fails, said the shadow minister, it would allow Labour "to then abstain" on the government's motion.
Without Labour support, David Cameron might struggle to win a Commons vote and commit to a US-led campaign of air strikes against the Assad regime. In June, 81 Tory MPs signed a letter to the prime minister demanding the right to veto any delivery of arms to the Syrian rebels.
The scale of disquiet over Syria inside Labour is growing and the Huffington Post UK has learned that both the Opposition Whips' office and the Labour leader's office have been ringing up backbenchers to canvass their views on military action.
An emergency meeting of the Parliamentary Labour Party (PLP) has been scheduled for 12.30pm on Thursday, two hours before the start of the Commons debate on Syria. The shadow cabinet will meet to discuss and decide the Labour line on air strikes at 10am. The shadow public health minister Diane Abbott, who isn't a member of the shadow cabinet, has said she would find herself in a "very difficult position" if Labour supported military action against Syria in the emergency vote planned for Thursday night.
On Tuesday evening, Miliband struck a hawkish note when he said "the use of chemical weapons on innocent civilians is abhorrent and cannot be ignored" and revealed that Labour "would consider supporting international action but only on the basis that it was legal, that it was specifically limited to deterring the future use of chemical weapons and that any action contemplated had clear and achievable military goals."
By Wednesday lunchtime, however, shadow foreign secretary Douglas Alexander was sounding much more sceptical and restrained than his leader: "We want to see the report of weapons inspectors...presented to the Security Council...prior to action being taken." Alexander also insisted the Attorney General's legal advice on Syria be published prior to the emergency debate in the Commons.
Shadow foreign secretary Douglas Alexander is sounding more cautious
"Douglas has been stiffening his position," says a senior Labour source. Meanwhile, adds the source, "Ed Miliband has gone to ground."
Some Labour backbenchers have privately expressed their frustration over the fact that Tory MPs have been much more vocal and public in their opposition to military intervention - though the former cabinet minister Peter Hain told the Guardian on Thursday that air strikes could be "very dangerous" and might drag the UK into "full-scale military action".
A senior Labour backbencher and close ally of Ed Miliband told HuffPost UK that too little attention has been paid to the "possible scenarios [of what happens] afterwards". "Knowing that something is legal doesn’t tell you whether it makes sense or not," he added.