MPs on the intelligence and security committee (ISC) have been criticised for failing to hold spy chiefs properly to account, following its first ever public hearing.

On Thursday afternoon Sir John Sawyers, the head of MI6, Andrew Parker, the head of MI5, and Sir Iain Lobban, the head of GCHQ, gave evidence to MPs in the wake of a series of revelations about the work of UK and US intelligence agencies. The spy chiefs used the session to attack The Guardian for publishing material obtained from NSA whistle-blower Edward Snowden.

It was the first time the British intelligence chiefs had given evidence to the ISC in public. The committee has been criticised for a lack of transparency and for not being able to properly oversee and scrutinise the work of the intelligence agencies. Holding a public session was seen as one way of demonstrating its effectiveness. It comes 38 years after the CIA Director first gave televised testimony to the US Congress.

The committee's chairman Sir Malcolm Rifkind said it was "a very significant step forward in the transparency of our intelligence agencies".

Tory Dominic Raab, a former Foreign Office lawyer, recently told The Huffington Post UK the committee was "weak" and too willing to believe what it was told by the intelligence agencies.

Following today's hearing he said: "For the first time, intelligence chiefs gave public evidence about the scope of their activities and powers. It punctures the myth that ensuring the agencies are more transparent and accountable comes at a price to UK national security. In fact, strengthening oversight will make the agencies more effective, preserve the rule of law and safeguard public confidence."

Several MPs and campaigners have also criticised the make-up of the body. And Sir Malcolm has had to defend his leadership of the committee against accusations of a conflict of interest. As a former foreign secretary, he was once in charge or MI6.

Reprieve criticised today's hearing as a "damp squib". The human rights campaign group's director Cori Crider said: "It gave a clear demonstration, if one were needed, of just how inadequate the ISC is as a watchdog on the intelligence services.

“They also failed to question GCHQ over its role in providing support to the CIA’s covert drone programme – which has killed hundreds of civilians in Pakistan and Yemen, and violates international law.

“The ISC’s inadequacy shows why the courts are so important to ensure abuses by the secret parts of the state are kept in check – yet the Government is doing its best to undermine our justice system, introducing secret courts and cutting back legal aid and judicial review. These moves must be resisted.”

Sir John Sawyers said Al Qaida and other terrorist groups have been "rubbing their hands with glee" over the information revealed by Snowden.

"The leaks from Snowden have been very damaging, they have put our operations at risk. It's clear our adversaries are rubbing their hands with glee, Al Qaida is lapping it up," he said. "I'm not sure the journalists managing this very sensitive information are very well placed to make those judgements."

Sir Iain Lobban was also deeply critical of the media for revealing how GCHQ worked. He said since the Snowden leaks were made public the electronic eavesdropping agency had seen "daily discussions" among its targets about how to avoid being tracked.

He said terrorist groups in the Middle East in Afghanistan and in South Asia had been heard discussing the revelations "in specific terms".

"We have seen chat around specific terrorist groups, including closer to home, discussing how to avoid what they now perceive to be vulnerable communications methods," he said. "The cumulative effect of the media coverage will make the job we have far, far harder for years to come."

Amid accusations that GCHQ is intruding too far into the private lives of innocent people, Sir Iain Lobban insisted his agents only targeted terrorists, criminals or foreign governments. "We do not spend our time listening to the telephone calls or reading the e-mails of the majority, that would bot be proportionate. It would not be legal, we do not do it," he insisted.

And he said were he to ask any of his officers to spy on innocent people they would quit. "If they were asked to snoop they wouldn't, half the workforce they would leave the building," he said. "I don't think secret means sinister."

The Guardian hit back at the criticism of its journalism following the session. A spokesperson for the newspaper said it was only the work of its reporters that had prevented a more "catastrophic leak" of secrets.

"The disastrous loss of classified data was not the responsibility of journalists but of the intelligence community itself. It is only the involvement of global newspapers that prevented this information from spilling out across the web and genuinely causing a catastrophic leak," the spokesperson said.

"We understand that the agencies will always warn that any form of disclosure has a damaging impact on their work – but this cannot mean the end of all questioning and debate."

The paper also criticised the questions asked by the MPs on the committee: "We welcome the fact that the intelligence chiefs acknowledged that they need to be more open as a result of the Snowden disclosures, but were surprised that unlike in the US and Europe there was no substantive discussion at all about anything Snowden revealed."

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Shami Chakrabarti, director of civil liberties and human rights campaign group Liberty, said: "These public servants presided over blanket surveillance of the entire population without public, parliamentary or democratic mandate.

"Yet they faced a grilling that wouldn't have scared a puppy. Broad, friendly questions were easily batted away and little was said that isn't already on public record. A real inquiry into this grand breach of trust must now begin."

Responding to complaints that the committee did not challenge the spy chiefs over renditions to Libya, a source close to the ISC pointed out that witnesses would have been unable to comment, as police investigations are under way.

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