The Prime Minister also said the government would “work up” laws for discretionary powers to ban suspect British nationals from returning to the UK.
Mr Cameron told MPs it was “abhorrent” British citizens who pledge allegiance elsewhere were able to return to the UK and pose a threat to national security.
The new powers will be introduced to bolster terrorism prevention and investigation measures (Tpims), including “stronger locational constraints”, he said.
The measures were announced yesterday by Mr Cameron as he confirmed 500 British citizens have joined the extremist jihadist group Islamic State (IS) operating in Syria and Iraq, and now pose a “serious” threat to the UK.
Among the other proposals the Prime Minister intends to bring forward are new powers to prevent aircraft from landing if they have not met strict new security criteria on passenger lists and terrorists being required to undergo de-radicalisation programmes.
In a statement to parliament, he also announced stronger powers on the relocation of terror suspects are to be re- introduced, sparking Labour heckles about the abolition of Labour-introduced control orders which allowed relocation of suspects but were replaced with weaker restrictions by the coalition.
There was also confusion over when the government would introduce the new measures, with a Downing Street spokesman insisting it would be “as swift as possible”, but unable to give a timetable for them.
With the key measure of refusing entry for British citizens suspected of being jihadists, the Prime Minister said talks with the security services would take place before he tried to find a “cross-party consensus”. However, he insisted the new powers were possible and could be introduced.
He told MPs: “We are clear in principle that what we need is a targeted, discretionary power to allow us to exclude British nationals from the UK and we will work up proposals on this basis with our agencies, in line with our international obligations, and discuss the details on a cross-party basis.”
This was met with questions from former Liberal Democrats leader Sir Menzies Campbell who outlined concerns such a move broke international law which says a person cannot be rendered “stateless”.
He was supported by Tory MP Dominic Grieve, who over the summer was sacked as attorney general by Mr Cameron.
Mr Grieve said: “Not only does it offend principles of international law, it actually would offend basic principles of our own common law as well.”
However, the Lib Dems claimed they had successfully watered down the proposals because of the international law problem. A senior party source said: “We cannot stop people returning forever. We have kicked it into the long grass.”
A new poll by ComRes of 1,001 adults suggests voters agree with Mr Cameron – with 61 per cent supporting preventing British terror suspects returning to the UK and just 29 per cent opposing it.
Outlining the terror threat level, which was raised to “serious” on Friday, Mr Cameron said thousands of EU citizens posed a risk and “holes in Britain’s security need to be plugged” although he insisted there will be “no knee-jerk reaction”.
Mr Cameron said the government would continue to assess what measures it would take in Iraq and Syria, including humanitarian and potentially military actions, that were in the national interest.
He said: “We have all been shocked and sickened by the barbarism we have witnessed in Iraq this summer, the widespread slaughter of Muslims by fellow Muslims, the vicious persecution of religious minorities such as Christians and Yazidis, the enslavement and raping of women and, of course, the beheading of American journalist James Foley with the voice of what seems to have been a British terrorist recorded on that video.”
Mr Cameron said at least 500 people had travelled from Britain to fight in the region – together with 700 from France, 400 from Germany and hundreds more from other states.
Mr Cameron added: “We should be clear about the root cause of this threat: a poisonous ideology of Islamist extremism that believes in using the most brutal forms of terrorism to force people to accept a warped world view and to live in a medieval state.”
On new measures to remove passports, Mr Cameron said passports “are not an automatic right”. He went on: “The Home Secretary already has the discretion to issue, revoke and refuse passports under the royal prerogative if there is reason to believe people are planning to take part in terrorist-related activity.
“But when police suspect a traveller at the border, they are not able to apply for the royal prerogative and so only have limited stop-and-search powers. We will introduce specific and targeted legislation to fill this gap by providing the police with a temporary power to seize a passport at the border.”
Labour leader Ed Miliband said the government’s move to get rid of so-called “internal exile” powers to relocate terror suspects in the UK a “mistake” and welcomed their reinstatement.
Mr Miliband welcomed plans to give police and border officers the power to seize passports, but said Mr Cameron’s proposals to exclude UK nationals involved in terrorism abroad from entering the country were “unclear”.
Mr Miliband also urged the Prime Minister to introduce a “mandatory and comprehensive” programme to de-radicalise both terror suspects and those who have been “on the fringes” of extremism in Iraq and Syria.
Former foreign secretary Jack Straw stressed the need “more than ever” of co-operation with Iran as one of the few stable states in the region. Mr Cameron was also told to “get on his hands and knees” and thank Labour for preventing Britain from arming Islamic extremists.
Analysis: Four contentious issues in PM’s proposals, writes Doug Weeks
To address the building wave of concern over British citizens travelling to Syria and Iraq becoming militarised and then returning to the UK where there is fear that they might attack, the Prime Minister made recommendations for new counter-terrorism measures to be instituted.
There are arguably four contentious issues in the Prime Minister’s proposals: first, to provide the police with temporary power to seize passports at the border; second, allow government the discretionary power to exclude British individuals from coming back to the UK; third, to amend the Temporary prevention and investigation measures (Tpims) to allow for “locational restaints”; and fourth, to mandate that those on TPIMs engage in the Channel programme.
The proposals by Mr Cameron culminate a steady build up of political rhetoric that has taken place over the past couple of weeks. And sadly, once again, the government’s actions reflect a reactive rather than proactive response.
At the core, there seems to be a belief that government can legislate itself out of this predicament by simply taking additional steps to further securitise the UK. And, rather than addressing the problem as to why young British citizens are radicalising in the first place and travelling abroad to fight, it is flexing its legislative muscle and criminalising its citizenry.
Although Mr Cameron did mention that some elements of his proposals would garner scrutiny such as the current challenges to the royal prerogative regarding passports, there seems to be several areas that were glossed over. For instance, extending additional power to the police to confiscate passports at a time when support for policing is already low within Muslim communities is not going to help that relationship. To bar UK citizens from coming back to the UK not only makes them stateless but is in conflict with existing international conventions.
To amend TPIMs to make them more like control orders is also highly problematic; not only were control orders highly damaging to the police in their community relationships, they were found to be in violation of Article 5 of the European Convention on Human Rights.
Although there is rightfully cause for concern about those travelling to Syria and Iraq and then come back to the UK, there is little statistical data to support that concern beyond two pending cases; one in Belgium and another in France.
Additionally, the government response of further securitisation plays into the hands of extremists who actively recruit members arguing that government measures are draconian. Until the government seeks to engage in a more holistic community based approach, the problem of radicalisation and associated threats of violence will continue unabated.
• Dr Doug Weeks is a Research Fellow at the Handa Centre for the Study of Terrorism and Political Violence at the University of St Andrews.