Secretive police trials of new technology which can access everything on our mobile phones are troubling, particularly when there is confusion over whether data was retained.

It has now been established that the hacking technology was used in pilots in Edinburgh and Stirling which saw officers trained and data from phones downloaded.

Details about the trial of the technology only emerged in response to a Freedom of Information request, which revealed police retained data and there could be further use of equipment.

In an apparent contradiction, a force spokesman ruled out using the technology again and said no data had been stored. This disparity must be cleared up to ensure public trust remains in tact.

Of course, many will believe police should be permitted to carry out investigations without hindrance and argue the innocent have nothing to hide.

However, there is a fundamental principle at stake - that the power of police should come from the consent of the public, not from the state. If officers can use technology to access phones without the knowledge of the user, how can there be consent?

Politicians and leading privacy campaigners have rightly called for independent oversight and suggest a warrant should be obtained by officers before phones are accessed in future.

What’s clear is that policing is changing rapidly to keep up with advances in technology, but the underlying principle of policing by consent should not be undermined. The use of a warrant to extract data from phones is a minimum requirement.