THE SNP have called for “honesty and transparency” from David Cameron after it emerged that he was aware of UK pilots being embedded with US forces in Syria as far back as last autumn.

It comes after Michael Fallon, the Defence Secretary, robustly rejected claims MPs were "kept in the dark" about the involvement of British pilots in airstrikes in Syria.

He told MPs this week it was "standard practice" for UK personnel to be embedded with allied forces, stressing how their engagement was not a "British military operation".

Last year, MPs backed UK airstrikes against so-called Islamic State fighters in Iraq but not in Syria. In 2013, they voted against taking any military action against the Assad regime.

The involvement of UK pilots in action over Syria, acting in co-operation with the US and other allied forces, only emerged because of a Freedom of Information request earlier this month.

In a parliamentary written answer to Brendan O’Hara, the SNP’s defence spokesman, the Prime Minister said embedding military personnel was a long-standing policy practised by many countries and he was “aware the Defence Secretary authorised the first embed with US forces in Syria in the autumn of last year”.

In response, Mr O’Hara, who represents Argyll and Bute, said: “This is more breath-taking arrogance from the UK Government on military involvement in Syria,” stressing how it showed Mr Cameron had “simply ignored” the 2013 MPs’ vote.

“It is becoming clear that far from a being a decision made within the last few weeks or months, this has been a long time in the planning, and the Government must now be absolutely clear about the timing and justification for this highly controversial military operation.”

Arguing the case for bombing Syria had not been made, Mr O’Hara added: “The Government's policy in this matter is entirely unacceptable - effectively overseeing a bombing campaign by stealth – and we urgently need honesty and transparency about precisely when it was authorised, who knew about it and when the Government was proposing to tell the country; if ever."

But Mr Fallon had insisted the embedding of the pilots in the country was "legal and necessary."