MOSCOW (Sputnik) - The ongoing legal challenge of UK human rights group Liberty over data privacy breaches committed by MI5 has revealed new details about the violations, showing that the security service has been failing to remove collected bulk surveillance data on time and received surveillance warrants based on knowingly false information.

Under the Investigatory Powers Act (IPA), MI5 has the authority to collect, upon authorization, personal data of a large number of innocent people and store it for potential future investigations. Security services, however, cannot store such data indefinitely: they are obliged to delete it within certain time limits.

Documents released during a court hearing on Tuesday showed that the MI5 legal team said, as quoted by the Liberty, that there is "a high likelihood [of material] being discovered when it should have been deleted, in a disclosure exercise leading to substantial legal or oversight failure."

Moreover, a senior official from the intelligence service said that people's personal data was being kept in "ungoverned spaces," the rights group said in a statement, published on its official website.

"These shocking revelations expose how MI5 has been illegally mishandling our data for years, storing it when they have no legal basis to do so. This could include our most deeply sensitive information – our calls and messages, our location data, our web browsing history," Liberty lawyer Megan Goulding said, as quoted by the rights group.

Investigatory Powers Commissioner and Lord Justice Adrian Fulford, who is responsible for verifying that the security services respect data privacy provisions laid out in the IPA, described MI5's actions as "undoubtedly unlawful."

"Without seeking to be emotive, I consider that MI5's use of warranted data ... is currently, in effect, in 'special measures' and the historical lack of compliance ... is of such gravity that IPCO [Investigatory Powers Commissioner’s Office] will need to be satisfied to a greater degree than usual that it is 'fit for purpose'" Fulford said as quoted by the Liberty website.

According to the rights group, the commissioner said that the intelligence would have never obtained permissions for their surveillance activities if the watchdog had known that MI5 was violating the IPA.

"Warrants for bulk surveillance were issued by senior judges (known as Judicial Commissioners) on the understanding that MI5's data handling obligations under the IPA were being met - when they were not," Liberty said.

The rights group raised the alarm about MI5's violations in May, prompting the investigatory powers commissioner to start an investigation into the matter.