THE prospect of British warplanes bombing IS positions in Syria appears to have moved closer after Michael Fallon gave the strongest hint yet, that in the wake of the Tunisia terror attack, the UK Government is considering extending air strikes across the Iraq border.

The Defence Secretary is likely to expand on the UK Government's developing thinking on the issue when he takes part in a Commons debate on Britain and International Security today.

He stressed that it was "illogical" that UK planes were able to hit extremists in Iraq but not bases across the border in Syria.

Last year, the House of Commons gave the go-ahead for the bombing of militant positions in Iraq but MPs were not asked to approve wider action. Ministers were mindful of how David Cameron had lost the vote in the last Parliament for air strikes in Syria following reports the Assad regime was engaged in chemical attacks on its own people.

Asked whether he thought British forces should now have the scope to strike IS targets in Syria, Mr Fallon replied: "There is an illogicality about not being able to do it.

"There were reservations in the last Parliament about doing anything in Syria that would prop up the Assad regime, which, of course, partly caused this problem in the first place...

"It is a new parliament and new MPs will want to think very carefully about how we best deal with IS, and the illogicality of IS not respecting the borderlines; they don't differentiate between Syria and Iraq, they are establishing this evil caliphate across both countries."

The change of approach has come about because of the terror incident in Tunisia.

One line of inquiry the local authorities, helped by police and security experts from the UK, are pursuing is that Seifeddine Rezgui, the 23-year-old gunman who murdered 38 people, including 30 Britons on a beach in Sousse, was trained by IS in Libya.

Whitehall insiders are keen to find out whether or not such a training camp - which potentially has trained or is still training other extremists - was co-ordinated by IS terror chiefs from their main base in Raqqa, Syria.

If a link could be proved, then the potential for the UK Government ordering RAF strikes to destroy a command and control centre at the heart of IS's operations would rise significantly.

Mr Fallon was keen to point out that the UK Government would be minded when considering any military action to seek parliamentary approval first.

"We have made it clear we would have to go back to Parliament, yes, and ask for parliamentary authority because we don't have that at the moment."

But he pointed out there was an exception to that process.

"As the Prime Minister has always made clear, where we think there is an imminent threat, a very direct one to British lives or, for example, to British hostages, then we reserve the right to take action without prior parliamentary approval and then coming to account for it afterwards."

Yet the Secretary of State also noted: "If we can link it(the Tunisia terror attack)...directly back to IS in Syria, then we will have to reflect with the rest of the coalition how best we deal with that."

Labour is indicating it might be willing to reconsider its position on airstrikes in Syria. Mary Creagh, who was an early challenger for the party leadership, said Labour had been wrong to rule out British bombing raids on IS in Syria last year.

Ministers believe the growing public revulsion about the extremists could persuade MPs to support a fresh military campaign in Syria.