"She took a decision sometime last week that she was going to work with Macron and Trump in order to have an attack on the chemical weapons establishment in Syria".
The prime minister, who spoke to Trump about the need to deter chemical weapon use in Syria in a phone call Thursday, is facing pressure from all sides to seek the backing of parliament.
He said a political solution needed to be found and that military strikes would not prevent further loss of life.
The government said it is "highly likely" that Assad is responsible for the Douma attack, with ministers agreeing "it was vital that the use of chemical weapons did not go unchallenged". French President Emmanuel Macron said Thursday France has "proof" Assad had used chemical weapons and was working closely with the USA on a possible response.
The US, UK and France hailed their missile strikes in the early hours of yesterday morning as having successfully degraded the capability of Assad to deploy chemical weapons.More news: PM Modi in Chennai says not biased against any region
First Minister of Scotland Nicola Sturgeon described the legal position as "thin", while BBC political editor Laura Kuenssberg noted that the United Kingdom is one of the few countries that tries to use humanitarian arguments to justify military action and most worldwide lawyers don't accept the contention.
Assad's government has denied it used chemical weapons on its own people, saying reports were "fabricated", BBC reported.
Evidence is still being gathered, but U.S. officials are understood to have results from blood and urine samples that indicate chlorine and a nerve agent were used in the Syrian town of Douma.
Labour say that the scheme would cost £1.4Bn per year, and that the party plan to pay for it by using money ring-fenced from Vehicle Excise Duty.
Russia's deputy prime minister, Arkady Vladimirovich Dvorkovich, hit out at Trump on Friday, saying global relations should not depend on the mood of one person when he wakes up in the morning, referring to the USA president's tweets on potential missile strikes into Syria.More news: Kentucky teachers claim victory as budget vetoes rejected
Earlier on Friday, Corbyn also accused May's government of "waiting for instructions" from the United States on how to proceed in the Syrian crisis, but that Donald Trump was giving "alarmingly contradictory signals".
Jeremy Corbyn has said he wants "incontrovertible proof" before blaming Russian Federation for the Salisbury nerve agent attack.
"In a modern, parliamentary democracy, I think you have got to have parliamentary approval if you have a planned, policy decision to launch a military attack of any significant size".
But he said it was "intellectually bankrupt" to expect the security services to lay out all the information they have.
He said: 'Parliament must be consulted on this.More news: Former US House Speaker To Promote Legalizing Marijuana