The government needs to be prepared to launch attacks on-line, according to one of the country's most senior security experts.

Professor Sir David Omand, a former GCHQ director, told MPs on Wednesday that the coalition "needs to be put more effort into the cyber domain".

"We too should be capable, should it come to it, to use the cyber domain for our own offensive purposes. For example in taking out an air defence system where we're engaged in military operations. We have to look not just at potential defence, but at potential offence," he said.

Speaking to the Defence Select Committee, Sir David warned that the government's cyber-security centre was insufficient.

"I question whether they have enough people with enough expertise," he said. "Will we be ahead of the curve and spot the next threat? I hope research is going into that."

The government's cyber security strategy was needed, Sir David said, in order to address the "vulnerabilities in a number of areas" to cyber attack.

And he warned that the government was "quite a small player" in terms of security capabilities. Speaking alongside Sir David, Professor Brian Collins of UCL warned that the UK government was vulnerable to many potential threats.

"I don't believe we have the mechanisms in place... to anticipate what could hit us" he told MPs.

This comes as highly-sensitive conversations between members of Mi6 and Scotland Yard were leaked by the hacking group TeaMp0isoN.

The government should also consider giving the police powers to intercept social media, Sir David suggested. He told MPs that, in light of last year's riots when rioters communicated via Facebook and Blackberry Messenger.

"They need to start thinking about the role of the police in being able to access social media in deriving intelligence to help for riots, crowd control and all the rest of it."

"There are lots of things... [the Government]...need to be thinking about now." he added.