See also: Picture profile of Met Police CIO Ailsa Beaton

Metropolitan Police Service (MPS) investigators will get quicker access to data from the mobile phones and smartphones of suspects after announcing the controversial deployment of the Radio Tactics ACESO data extraction system.

Sixteen of the capital's inner and outer boroughs will start using the technology this summer, allowing officers to access to data held on phones within minutes rather than having to send each device them away for expensive, specialised analysis.

The ACESO system comprises a touchscreen acquisition tool that can be used by trained frontline officers. Having such a system in police stations makes it possible for officers to act on phone data while a suspect is still in custody, Radio Tactics said.

"Mobile phones and other devices are increasingly being used in all levels of criminal activity," said MPS deputy assistant commissioner, Stephen Kavanagh.

"When a suspect is arrested and found with a mobile phone that we suspect may have been used in crime, traditionally we submit it to our digital forensic laboratory for analysis. A solution located within the Boroughs that enables trained officers to examine devices and gives immediate access to the data is welcomed," said Kavanagh.

SMS texts, images and phone numbers helped police to quickly identify arrested individuals, he said.

The MPS told the BBC that extracted data would be retained by the police even if the suspect was released without charge, which has sown a seed of controversy as to how it will be used.

Officers would only extract data if they suspected it might hold evidence of criminality. What remains less clear is the conditions under which suspect would be forced to reveal phone security PIN numbers and how long data discovered during investigations would be retained.

'We need a full and frank disclosure of how and when and why this system will be used,' said Emma Draper of campaigning group, Privacy International.

"It is illegal to indefinitely retain the DNA profiles of individuals after they are acquitted or released without charge, and the communications, photos and location data contained in most people's smartphones is at least as valuable and as personal as DNA," she told the BBC.

Longer term, rapid data extraction could also encourage the use of encryption technologies on smartphones, putting the police use of such technologies back to square one.

The ACESO system supports data extraction from a wide range of handsets including many common smartphones.