Business Secretary Vince Cable has called for "proper political oversight" of the UK's intelligence services after revelations of the extent of eavesdropping carried out by British listening post GCHQ.
The Liberal Democrat minister said the Guardian newspaper had performed "a very considerable public service" by publishing secret material leaked by whistle-blower Edward Snowden, which exposed surveillance programmes run by the US National Security Agency in conjunction with GCHQ.
Cable confirmed reports that Deputy Prime Minister Nick Clegg was looking into an overhaul of intelligence service oversight by politicians.
He told the BBC's Today programme: "I think Mr Snowden's contribution is twofold, one of which is a positive one - which is whistle-blowing - and the other of which is more worrying: that a large amount of genuinely important intelligence material does seem to have been passed across."
The American journalist behind the security leaks that prompted criticism from MI5 director general Andrew Parker has firmly denied helping terrorists.
Glenn Greenwald told ITV News it was "a complete lie" that the information he obtained from the former National Security Agency contractor Edward Snowden taught terrorists anything they did not already know.
The Guardian journalist, who gave evidence to Brazil's senate on the matter today, told ITV News' Brazil correspondent Nick Ravenscroft: "It's an absolute fabrication ... There is not one thing that we published that gives any kind of guide".
How much damage have Edward Snowden's revelations caused to British national security?Read the full story ›
Following criticism of the Guardian publishing details of secret documents leaked by former NSA worker Edward Snowden as handing "a gift to terrorists", a spokeswoman said:
A huge number of people - from President Obama to the US director of national intelligence, James Clapper - have now conceded that the Snowden revelations have prompted a debate which was both necessary and overdue.
The President has even set up a review panel and there have been vigorous discussions in the US Congress and throughout Europe. Such a debate is only worthwhile if it is informed. That is what journalism should do."
In response to the Daily Mail's story which quotes 'Whitehall insiders' as saying the Guardian's Edward Snowden leaks caused the "greatest damage to western security in history, the newspaper's editor Alan Rusbridger tweeted:
It comes after the Director General of MI5, Andrew Parker said that leaks such as those from former NSA worker Snowden gave terrorists the, "gift they need to evade us."
Terrorism is "no longer over there, it's here" according to a security expert.
Dr Sally Leivesley told Daybreak terrorists were frequently fighting abroad in countries like Syria and Afghanistan, "learning the trade" and then returning to England.
Dr Leivesley was speaking after the head of the MI5, Andrew Parker, went on a blistering attack against Edward Snowden and the Guardian for exposing America and Britain's mass-surveillance programme.
"It is quite interesting because he [Parker] talks about why we have to live without fear and it's why he..tries to dull down the statements that he is making, because he is really telling us we have to expect this.
"But he is also saying that it is so unpredictable that they can't tell if they are going to be successful against these attacks, because the whole of policing, is lifted off up the ground.
"It is no longer just the police on the street. It is really through the airwaves."
The Daily Mail has taken a swipe at the Guardian after the Director General of MI5, Andrew Parker said that leaks such as those from former NSA worker Snowden gave terrorists the, "gift they need to evade us."
Nick Pickles, director of civil liberties campaigners Big Brother Watch, said:
This speech is more striking for what it did not say.
No recognition that Britain's legal framework was drawn up before Google existed, no acknowledgment that our antiquated oversight mechanism may need further reform, no mention of the US Government's moves towards increased transparency and oversight.
The fact he does not feel GCHQ's reach should be publicly discussed is in stark contrast to the US government's efforts to maintain public confidence by bringing further transparency and oversight to the reach of the NSA.
People will rightly question why, if the US congress can publicly debate the reach of their agencies, the British public should be denied any details of what is happening here.
The Director General of MI5 has warned of the increased risk of terrorism from Syria.
Speaking in public for the first time Andrew Parker said there was a "growing concern" over the troubles country:
"For the future, there is good reason to be concerned about Syria. A growing proportion of our casework now has some link to Syria, mostly concerning individuals from the UK who have travelled to fight there or who aspire to do so"
The Director General of MI5, Andrew Parker, has warned about the risks of Islamists in the UK.
Addressing the Royal United Services Institute (RUSI), Mr Parker said:
Since 2000, we have seen serious attempts at major acts of terrorism in this
country typically once or twice a year. That feels to me, for the moment, unlikely to change.
While that tempo seems reasonably even, the ground we have to cover has increased as the threat has become more diversified.
The ability of Al Qaida to launch the centrally directed large scale attacks of the last decade has been degraded, though not removed. We have seen the threat shift more to increasing numbers of smaller-scale attacks and a growing proportion of groups and individuals taking it upon themselves to commit acts of terrorism. It remains the case that there are several thousand Islamist extremists here who see the British people as a legitimate target.