GCHQ file leaks caused “enormous damage” : MI5 chief

Sounding a warning, the new head of MI5 said the leaks of thousands of GCHQ files by CIA spy Edward Snowden had caused ''enormous damage'' and handed terrorists the ''gift'' to attack the UK ''at will''.

According to the director general of the security service, Andrew Parker, the exposing of intelligence techniques, by The Guardian, had given fanatics the ability to evade the spy agencies.

The renewed threat came even as the UK was faced with its gravest terror threat, including from ''several thousand'' Islamist extremists who were living in the country and wanted to attack it, Parker said.

Parker used his first public outing since taking over at MI5 to launch a scathing attack on the Snowden leaks.

Leaks from Snowden are known to contain at least 58,000 GCHQ files and it was feared there could be many more.

It was also not clear whether foreign states had access to the documents and The Guardian is believed to have continued to expose the information despite pleas from the government not to reveal intelligence techniques.

It was believed to be the worst leak of British intelligence files and had caused the greatest damage.

In his first speech since taking over as head of MI5, Parker did not specifically name Snowden or The Guardian, but said it caused enormous damage to make public the reach and limits of GCHQ techniques.

He warned that terrorists could now use tens of thousands of means to communicate "through e-mail, IP telephony, in-game communication, social networking, chat rooms, anonymising services and a myriad of mobile apps".

According to Parker, it was vital for MI5 - and by inference its partner GCHQ - to retain the capability to access such information for the protection of the country.

However, some had argued that Snowden's revelations, which were published in the newspaper, had not harmed the UK, and in fact, opened a debate on the balance between privacy and security.

According to Henry Porter, a columnist with that newspaper's sister title The Observer, the people who had released and let go of the documents, of course, were the NSA in America where the leak took placed and the newspaper had not published anything that jeopardised the security of this country.

He said in an with BBC Radio 4's Today programme, that what the newspaper had done was to show how much surveillance citizens were under legitimately under laws that have been passed by the government.