Police forces have been urged to keep better records on how much data they slurp from the hundreds of thousands of digital devices they seize, and how it is used.

Campaign group Big Brother Watch issued the demands after a largely unsuccessful mission to assess just how much data the forces extract from devices they've seized as evidence.

The group sent a series of Freedom of Information requests to the 45 forces in the UK, and 93 per cent reported that, yes, they did extract data from the devices they brought in.

However, when asked for more information - such as how many devices were recovered and how many of those had had data extracted from them - 71 per cent declined to comment.

Twenty-two of the 32 refusals said the information wasn’t held in an "easily retrievable format" and 10 said it would require a manual search to get it.

In a report published today, Big Brother Watch said that such responses "are simply not acceptable", arguing that they undermine policing good practice principles that call for transparency.

"Records of the number of seized devices, the number of devices subject to data extraction and details regarding how long data is held for must be kept and made available for audit," the report said.

Of the forces that did respond, the results showed that 149,203 devices were recovered as evidence by 11 forces between 2013 and 2016. West Yorkshire Police were the most eager collectors, amassing 28,808 devices during that time.

Meanwhile, across nine forces, some 156,595 devices were subject to data extraction, with Police Scotland scraping 52,560 devices during 2013-2016.

Part of the problem, as BBW sees it, is that the legislation governing the way the police handles digital information is outdated.

It acknowledged the importance of such evidence in police inquiries, but said that by amending existing laws, the government had created a “far from technically detailed framework” that didn’t properly address the complexities of new tech.

The campaign org also raised concerns about training for forces, pointing to previous reports from watchdog Her Majesty's Inspectorate of Constabularies that said officers are “overwhelmed” when it comes to digital evidence.

Of the 14 forces that responded to questions on staff training budgets, the Met - the largest force in the UK - was at the top, with an annual budget of £130,000 between 2013 and 2016. It also paid £8.7m to third party services for digital forensics.

In contrast, City of London - one of the smallest forces in the UK - had a budget of £63,175, with just 16 officers trained in digital forensics. That this force is focused on fraud and economic crime, which are increasingly online crimes, “is of particular concern”, the campaign group said.

Norfolk and Suffolk constabularies had a joint budget of £20,000 for the 2013-16 period, but they also more than quadroupled the number of officers trained in data extraction in the last year: from 25 in 2015 to 109 in 2016.

Big Brother Watch acknowledged the differences in sizes of force, but criticised what it described as "patchy" training.

It called for more investment in training in both the technical aspects and data protection laws, "to ensure that the 'skills gap' is kept to a minimum, and that officers are prepared to deal with new evolving technologies". ®