However, there was criticism from Labour, UKIP and the SNP, and some within the Conservative party.

That’s the question troubling many MPs, not all of them on opposition benches.

Airstrikes are being conducted without parliamentary approval, Reprieve learned through a freedom of information request. They were under foreign command.

The UK Ministry of Defense has responded to the revelation by saying that “the United Kingdom is not conducting airstrikes in Syria”.

Britain has been providing limited support to coalition military action in Syria, carrying out refueling and surveillance operations over the country, the Telegraph reported.

These personnel include pilots flying… strike missions against Isil targets using the equipment of those units. “Of these three nations, only the US and Canada are operating in Syrian airspace”.

The Ministry of Defence released the information in response to a request from human rights group Reprieve. MPs rejected possible military action against Assad Regime in Syria in August 2013.

In 2013, lawmakers in the House of Commons rebuffed Prime Minister David Cameron’s call for a strong response to allegations the Syrian government had used chemical weapons.

Mr Baron added: “Those troops or individuals should be withdrawn from the embedded programme whilst this vote holds sway, while it stills hold authority, until we vote again”.

Labour, which recently indicated it could be prepared to back a fresh vote on extending air strikes into Syria, said that it would be calling on ministers to make a Commons statement on Monday about the role British pilots had played. Vernon Coaker, the shadow defence secretary, said there was “huge sensitivity” around granting permission for strikes in Syria, yet MPs had been kept in the dark.

Alex Salmond MP, the SNP’s foreign affairs spokesperson, said the government had been effectively overseeing a “bombing campaign by stealth”.

New Liberal Democrat leader Tim Farron said the involvement of RAF pilots in air strikes without the approval of Parliament was “a breach of trust with the British people” that would simply play into the hands of IS – also referred to as Isis or Isil. Commentators said a new vote would be likely to succeed.

“Stop the War demands the government publicly commits to an immediate end to British bombing of Syria”, the organization continued.

The U.S. and five Arab allies launched the first strikes against IS militants in Syria in September past year. However, MPs were not asked at the time to authorise strikes across the border in Syria.