Theresa May has joined with Emmanuel Macron and Donald Trump to say the international community must respond to uphold the ban on chemical weapons in the wake of the Syria attack.

The three leaders have held separate phone calls to discuss their response to the reports Bashar Assad used the banned weapons on his own people - killing dozens.

The world is waiting to hear what their response will be as the US President is expected to order air strikes on Syria in retaliation.

The high-level talks come after Tony Blair called for the PM to take military action a against Syria without holding a vote of MPs in Parliament.

But Commons defence committee chairman Julian Lewis told MailOnline there should be a vote before strikes.

A Downing Street spokesperson said: 'They agreed that reports of a chemical weapons attack in Syria were utterly reprehensible and if confirmed, represented further evidence of the Assad regime's appalling cruelty against its own people and total disregard for its legal obligations not to use these weapons.

'They agreed that the international community needed to respond to uphold the worldwide prohibition on the use of chemical weapons.

Theresa May (pictured today at Addenbrooke's Hospital in Cambridge) has spoken to Emmanuel Macron and will have a call with Donald Trump later as the allies plot retaliation against Syria

The PM held talks with Emmanuel Macron and Donald Trump on the phone today amid growing speculation that a Western coalition is being put together to strike back at Assad for the chemical attack

'They agreed they would continue working closely together and with international partners to ensure that those responsible were held to account.'

Mrs May confirmed today on a visit to Cambridgeshire that Britain was working with allies and partners to establish exactly what happened in Douma on Saturday.

Momentum is building behind Western retaliation for the chemical weapon strike.

Does May need to call a Commons vote on striking Syria? Theresa May was constitutionally entitled to order British forces into action in Syria without a Commons vote. The Prime Minister has the power to deploy troops under the Royal Prerogative. There are no hard and fast rules obliging the government to involve rank-and-file MPs in the decision. But a vote on prolonged deployment of UK forces would be almost impossible to avoid. Commons divisions have been held on almost all military action by British forces since the Iraq War in 2003, establishing what many see as a firm convention. Advertisement

The PM today condemned the 'barbaric' attack and warned those responsible would be held to account.

Downing Street has said questions of military action remain hypothetical but all options are on the table if Syrian culpability is proven.

The National Security Council meeting this afternoon came after Mr Tony Blair backed Western military action against the Syrian regime over chemical attacks on civilians.

The former PM urged Mrs May to be 'supportive' of strikes expected to be launched by Mr Trump in the coming days and said she did not need a Commons vote on strikes.

If Mrs May does decide she wants to join coalition action she will have to decide whether to ask MPs for permission to send UK forces into action. She swerved questions on calling a vote by MPs.

Speaking in Cambridge today, Mrs May said: 'This attack that took place in Douma is a barbaric attack.

'Obviously we are working urgently with our allies and partners to assess what has happened on the ground.

'If this is the responsibility of Assad's regime in Syria then it's yet another example of the brutality and brazen disregard for their people that they show.

Britain has a variety of military options it could bring to any action against President Assad's regime in Syria

Mr Blair told BBC Radio 4's Today programme: 'I think it is important, provided that our advice about the source of the attack is the same as that of US, that we would support US action.

'Meaning if the US are taking action we should be prepared to be alongside them.'

Mr Blair said it was possible to draw a distinction between air strikes and deploying troops in terms of whether to call a Commons vote.

He said: 'I think in circumstances where the action presumably would be a form of air action rather than ground force action, I don't think strictly it's necessary.

'I think this is something that she can consider.'

He added: 'I think if the Americans are prepared to act and are going to act fast, I think ourselves, probably the French government will be in the same position, should be supportive.

'It's important that when chemical weapons are used in this way and the international community has taken a firm position against it that you have to enforce it.'

Mr Lewis told MailOnline there should be a vote before strikes. He said: 'When our country comes under attack then the Government may have to act first and seek Parliament's approval afterwards.

Tony Blair (pictured in London today) today backed Western military action against the Syrian regime over chemical attacks on civilians

'When we are contemplating military intervention in other people's conflicts, Parliament ought to be consulted first.'

But there are splits within the Conservative party's ranks as Tory MP and Army veteran Johnny Mercer today called on Mrs May to order strikes without a vote.

Writing in the Sun, he said: 'We elect a government and we elect a Prime Minister to make these decisions. They have all the facts, all the high-level security briefing, assimilate all the evidence then act in the national interest. That's what they get paid for.

'Going through Parliament is a cop-out on that responsibility.

The US is expected to repeat missile strikes (pictured during last year's attack) on Syria

'And then we act. Anyone involved in the decision-making process of using chemical weapons in Syria must be targeted. They cannot be allowed to rest easy.'

Votes have been held on almost all military action by British forces since the Iraq War in 2003.

Forces were deployed to support the French in Mali in 2013 without a vote and David Cameron ordered a drone strike on ISIS in Syria in 2015 without giving MPs advance notice.

But MPs voted against military action against the Assad regime in 2013, meaning Mrs May will be under acute pressure to call a vote to join any strikes.

David Cameron called the 2013 vote believing he had the support of Ed Miliband - but the Labour leader changed his mind and led his MPs into the No lobby, along with 30 Tories. Mr Cameron lost the vote by 13.

Mr Trump has warned he will respond to the attack within hours and talks have been held between Britain, France and America on exactly what action to take.

A meeting of the UN Security Council descended into farce last night as the Russian government supported its ally in Syria.

Mr Blair said Western Governments had to act in response to the attack, thought to have killed dozens of civilians including children.

This image released early Sunday, April 8, 2018 by the Syrian Civil Defense White Helmets, shows a child receiving oxygen through respirators following an alleged poison gas attack in the rebel-held town of Douma, near Damascus, Syria

He warned: 'When you intervene it is extremely difficult but when you don't intervene it is also difficult.'

In other developments, Tory former foreign secretary Lord Hague said he had 'little doubt' that if he was still in office he would recommend military action in Syria.

Lord Hague, who was foreign secretary when then prime minister David Cameron lost a Commons vote he wanted to back action in Syria, said the aftermath of the defeat left the UK 'enfeebled spectators of one of the most destructive conflagrations of our time'.

Writing in The Daily Telegraph, Lord Hague said: 'We were left with only words, and compared to other nations financing armies or sending forces, words count for very little.

Tory former foreign secretary Lord Hague said he had 'little doubt' that if he was still in office he would recommend military action in Syria.

'We should have learnt from the fiasco of 2013 that abdication of the responsibility and right to act doesn't make war go away.'

Russia has warned that US military action in Syria in the wake of an apparent poison gas attack could cause 'grave repercussions'.

Moscow's ambassador to the UN made the comments after US president Donald Trump said on Monday he would decide on a response to the 'heinous attack' on Douma within 24 to 48 hours.

In heated exchanges at the UN Security Council, US ambassador Nikki Hayes accused Russia of having 'the blood of Syrian children' on its hands.

Following remarks by Mr Trump that 'nothing's off the table' as he meets with military advisers to decide America's response, Russian ambassador to the UN Vassily Nebenzia said US attacks on Syria 'could lead to grave repercussions'.

Mr Nebenzia dismissed claims the Syrian regime had used chemical weapons as 'fake news' as he called for inspectors from the Organisation for the Prohibition of Chemical Weapons to fly to Syria on Tuesday to visit the site of the alleged attack.

Ms Haley urged the UN to take action, but stressed whether it acts or not 'either way, the United States will respond'.

She added: 'Meetings are ongoing. Important decisions are being weighed, even as we speak.'