MOST people in the UK are opposed to Britain becoming engaged in any type of military action against Islamic extremists in Iraq and Syria, a new poll has found.

The strong opposition comes as David Cameron announced new measures to allay public fears in light of the heightened security level but left open the door to British air-strikes against the militants of Islamic State(IS).

A Comres telephone survey of 1000 adults undertaken over the weekend showed 50 per cent of people were against the UK launching airstrikes with 35 per cent in support. Opposition to the use of British ground troops was even stronger with 69 per cent of respondents against and only 20 per cent for.

On security measures, 61 per cent supported the removal of passports and citizenship from Britons suspected of joining IS with 29 per cent opposed.

In a Commons statement, the Prime Minister announced the police would be given temporary powers to seize passports at UK borders of those Britons suspected of travelling abroad to fight with terror groups.

Airlines would face tougher rules, legally obliging them to hand over passenger lists to help identify Islamist fighters; refusal would result in their flights being blocked from landing in the UK.

In an apparent U-turn, he also said powers to relocate terror suspects would be introduced, reinstating a key part of control orders, which were abandoned by the Lib-Con coalition earlier in this Parliament.

All these measures would require fresh legislation, which, No 10 said, would be enacted "as swiftly as possible".

But on the contentious issue of removing the passports of those suspected jihadists coming back to Britain from Iraq and Syria, there was no firm conclusion. Whitehall sources made clear this was a complex legal area and that there would be "further detailed consideration" of the issue.

Mr Cameron said it was "abhorrent" that British citizens, who pledged allegiance elsewhere, were able to return to the UK and pose a threat to national security.

"Adhering to British values is not an option or a choice. It is a duty for all those who live in these islands so we will stand up for our values, we will in the end defeat this extremism," declared the PM.

He dismissed as "wrong" suggestions by London Mayor Boris Johnson that travel to certain countries should be criminalised but said measures were needed to stop some Britons returning.

"We will introduce new powers to add to our existing measures, including stronger locational constraints on suspects under TPIMS (Terrorism Prevention and Investigation Measures) either through enhanced use of exclusions zones or through relocation powers."

Labour leader Ed Miliband picked up on the relocation powers, telling the PM: "With regards to the most serious high-risk cases where convictions in the courts cannot be achieved, I welcome your recognition that the independent reviewer on terrorism had made clear the inadequacies of TPIMS; in particular, the inability to relocate suspects".

Mr Miliband also stressed Mr Cameron's proposals to exclude British nationals involved in terrorism abroad from entering the country were "unclear".

Later, former Attorney General Dominic Grieve said while returning British jihadists could be tried for treason in the UK, there would be "very severe difficulties" in excluding them from returning altogether. He admitted it would be "probably impossible".