British spy agency MI5 ran a programme to collect data that was 'so secret that few even in MI5 knew about it'

MI5, the domestic arm of the UK's counter-intelligence and security agency, has been collecting, and analysing, the phone records of citizens for 10 years, the BBC reports.

The programme was based on "vague" laws, according to the government's terror watchdog, and Home Secretary Theresa May's new bill seeks to firm up the basis on which the government can spy on its citizens.

The new bill, which is titled "The Investigatory Powers Bill," seeks to give MI5, MI6, and the police more power when it comes to collecting and analysing the digital communications of UK citizens by suring up the law. May made reference to the 1984 Telecommunications Bill which gave the government powers to access data from communications companies during her speech in Parliament.

The BBC's Gordon Corera described the the activities of MI5 as "so secret that few even in MI5 knew about it, let alone the public."

The government-appointed reviewer of the legislation described the law as "so vague that anything could be done under it." The UK government's actions were not illegal because "the law was so broad and the information was so slight that nobody knew it was happening," he said.

According to May, the new Bill is a departure from the "Snooper's Charter," which was killed by the Liberal Democrat Party. Andy Burnham, the shadow home secretary, described the new bill as "neither a snoopers' charter nor a plan for mass surveillance."