MOUNTING speculation over what action Theresa May has decided to take on the alleged chemical attack in Syria was met with silence from Downing Street yesterday.

A statement released late on Thursday night, after May met with and gained support from her Cabinet, would only say it was “vital that the use of chemical weapons did not go unchallenged” and that there was a “need to take action to alleviate humanitarian distress and to deter the further use of chemical weapons by the Assad regime”.

There was, at the time of going to print, still no public statement on what that action might involve.

Opposition politicians suggested it was because the Prime Minister was waiting for orders from Donald Trump.

SNP defence spokesman, Stewart McDonald tweeted: “It’s almost 24 hours since the UK Government agreed a position on Syria. Parliament and the public are still none the wiser about what they wish to do.

“There hasn’t even been a briefing of privy councillors. Why? Theresa May is waiting on President Trump.

“He calls the shots now.”

Labour leader Jeremy Corbyn took a similar line: “More bombing, more killing, more war will not save life. It will just take more lives and spawn the war elsewhere.”

He added: “The Government appears to be waiting for instructions from President Donald Trump on how to proceed.

“Britain should press for an independent UN-led investigation of last weekend’s horrific chemical weapons attack so that those responsible can be held to account.”

May and Trump spoke by phone on Thursday night. Downing Street said the two had “agreed that the Assad regime had established a pattern of dangerous behaviour in relation to the use of chemical weapons”.

The spokesman for No 10 added: “They agreed it was vital that the use of chemical weapons did not go unchallenged, and on the need to deter the further use of chemical weapons by the Assad regime. They agreed to keep working closely together on the international response.”

At an emergency meeting of the UN Security Council, yesterday US ambassador Nikki Haley said the Americans had still not decided on what action they will take: “Our President has not yet made a decision about possible action in Syria. But should the United States and our allies decide to act in Syria, it will be in defence of a principle on which we all agree.

“All nations and all people will be harmed if we allow Assad to normalise the use of chemical weapons.”

Trump said yesterday he would take a decision on action against Syria ‘‘fairly soon’’.

Earlier this week he suggested missiles would be fired but then said that could happen ‘‘very soon or not so soon at all’’.

Moscow’s ambassador to the UN, Vassily Nebenzia, said the threat of military action in Syria was an attempt to contain Russia. “We continue to observe dangerous military preparations for an illegal act of force against a sovereign state in what would constitute a breach of international law.

“We call on the leadership of these states to immediately reconsider.

“The sole thing they have an interest in is to oust the Syrian government and more broadly to contain the Russian Federation.”

May is due to make a statement to the House of Commons on Monday, but there have been calls to change the business arranged for Parliament so that MPs can have full-scale debate and vote on intervention.

And, if it does go to a vote, there are increasing signs the Prime Minister will not have the support of all her own backbenchers.

Bob Seely, the Isle of Wight Conservative MP, told a daily newspaper: “The Government owes it to Parliament to come and explain.”

“Articulating their case in a chamber full of critical voices is good for the Government. If it can’t, then maybe it shouldn’t be doing it.”

Dominic Grieve, the former Tory attorney general, said: “If it all goes terribly wrong then the Government will be in difficulties. It will then have chucked at it that it hasn’t consulted Parliament.

“The pressure on government to hold a debate in government time is going to become overwhelming. Parliament can’t just be left sitting on the sidelines.”

Johnny Mercer said MPs would not be able to make a proper decision about what should happen as they don’t have the same access to intelligence as the Prime Minister and the National Security Council.

MPs “absolutely must have their say”, he said, “but the idea that that is binding and the Prime Minister then has her freedom of movement limited by not going to Parliament is not good for the country and not the right thing to do”.

Legally, May does not need approval from Parliament to deploy the armed forces, as that comes under the Royal Prerogative.

However, after Tony Blair, asked for MPs to agree to the invasion of Iraq of 2003, there is now a constitutional convention that a government should secure the backing of the Commons before starting a military operation.

When David Cameron asked Parliament in August 2013 for permission to take military action against Syria, he was defeated, and then ruled out joining in with US led air strikes.