Image caption The unrest in Syria might be exploited by "al-Qaeda elements", the committee warned

Al-Qaeda could gain access to Syria's stockpiles of chemical weapons with "catastrophic" consequences, a parliamentary committee has warned.

The Intelligence and Security Committee's annual report said spy chiefs considered this UK's "the most worrying emerging terrorist threat".

They also had no doubt that "vast stockpiles" of chemical weapons had been amassed in Syria, the ISC said.

Al-Qaeda and "individual jihadists" were both seen as threats, it added.

"There is a risk of extremist elements in Syria taking advantage of the permissive environment to develop external attack plans, including against Western targets," the ISC, which oversees the work of the intelligence agencies, said in its annual report.

Protests in Syria, inspired by the Arab Spring which saw changes of government in Tunisia, Egypt and Libya, were brutally suppressed by security forces in 2011.

The stand-off has since escalated into a civil war which has claimed tens of thousands of lives so far, according to UN estimates.

'Deadliest'

Analysis The annual ISC report provides a unique insight into the work of Britain's intelligence agencies - but it has its limits. It makes clear that cyber is moving up the agenda, although terrorism remains the biggest concern thanks to the impact of Syria and the danger of chemical weapons getting into the wrong hands. More is being done in conjunction with allies to the point where the committee was told that, in the recent campaign in Libya, Britain "went to war on German maps". There is also the intriguing fact that MI6 is questioned over a payment of several million pounds "relating to an operation with a foreign intelligence service which was not adequately documented". No more detail on this, nor on two of the most controversial issues of recent months: the killing in Woolwich of Lee Rigby and revelations by Edward Snowden about GCHQ. Those issues are being looked at separately.

After hearing evidence from senior members of the intelligence agencies and the Joint Terrorism Analysis Centre (JTAC), the committee highlighted "serious concern" among its witnesses that Syria's weapons stockpiles might be compromised.

Assessments of their contents "vary considerably", the report said, but suggest they include sarin, ricin, mustard gas and VX, which the committee described as "the deadliest nerve agent ever created".

"There has to be a significant risk that some of the country's chemical weapons stockpile could fall into the hands of those with links to terrorism, in Syria or elsewhere in the region," the committee concluded.

"If this happens, the consequences could be catastrophic."

The ISC also warned: "Large numbers of radicalised individuals have been attracted to the country, including significant numbers from the UK and Europe.

"They are likely to acquire expertise and experience which could significantly increase the threat posed when they return home."

'Frontline capabilities'

The report said there was a growing threat of attacks by "lone actors", like the assailant who stabbed Labour MP Stephen Timms while he was holding a surgery in his east London constituency in 2010.

By their nature, lone actors are much harder for intelligence agencies to detect, it added.

One Home Office official reportedly told the committee: "There is no doubt that the more sophisticated people in al-Qaeda recognise that groups are, in some ways, a thing of the past; and that encouraging lone acts of terror is exactly the way forward."

The ISC expressed concern that the agencies were struggling to make projected efficiency savings, due to be completed by 2014-15.

It highlighted a forecast £59m shortfall in the £220m savings that the agencies - MI5, MI6 and GCHQ - were supposed to have achieved through more collaborative working.

While the agencies said they were "fairly confident" that the targets set by the Treasury would be met, the committee said it "does not fully share that confidence".

The committee said: "It is essential that real and sustainable efficiencies are delivered if frontline capabilities are to be protected. More needs to be done urgently."