Scotland Yard has been asked to inspect thousands of files that could reveal whether its officers unlawfully procured mobile phone-tracking data for News of the World reporters.

There were half a million requests by public authorities for communications data in the UK last year – of which almost 144,000 were demands for "traffic" data, which includes location.

A Metropolitan Police Authority (MPA) member has asked the force to investigate allegations that News of the World reporters were able to purchase this data from police for £300 per request.

The claims were made by Sean Hoare, the News of the World whistleblower, days before he was found dead at his home on Monday. His disclosure about the purchase of illicit location data was first made to the New York Times, which said the practice was confirmed by a second source at the tabloid. Police have said Hoare's death was not suspicious.

Mobile phone location data, which is highly regulated, would give tabloid reporters access to a method of almost total surveillance, arguably even more intrusive than hacking into phone messages.

Jenny Jones, a Green party member of the MPA, has written to the commissioner requesting an audit of all cases where the Met obtained tracking data from mobile phone companies.

She has also asked the commissioner to guarantee that anyone with reason to suspect a tabloid may have gleaned their whereabouts from their mobile phone signal will have their case looked into.

Two police surveillance sources with knowledge of the system said location data was routinely used by police. Both said any corrupt purchase of information would require a fabricated request under the Regulation of Investigatory Powers Act (Ripa) and therefore the knowledge of a senior officer.

The Met and other forces have central databases where they record Ripa authorisations for audits by the interception of communications commissioner. Police are also compelled to keep Ripa authorisations files under the same rules that compel them to keep evidence connected to criminal investigations, which in some cases can mean paperwork is stored for decades.

Records are also kept by mobile phone providers, with at least one company maintaining an "indefinite" database of Ripa requests since 2009.

This detailed audit trail contrasts with the paucity of evidence in cases of phone hacking, due to the fact that records of phone activity are generally destroyed after 12 months.

The New York Times first reported that the News of the World may have had access to phone-tracking data last week, days before Hoare's death.

It said Hoare, a reporter who was sacked from the News International title in 2005, alleged that his editor Greg Miskiw could locate information about a person's precise whereabouts via their mobile phone number.

Hoare claimed that Miskiw had once helped him locate a person in Scotland, and said the information came from "the Old Bill".

The following day he told the Guardian that reporters would ask a news desk executive to obtain the location of a target: "Within 15 to 30 minutes someone on the news desk would come back and say: 'Right, that's where they are.'"

He added: "You would just go to the news desk and they would come back to you. You don't ask any questions. You would consider it a job done."

Hoare made no reference to which police force may have sold the data, although the Metropolitan police are currently investigating evidence that corrupt officers from within its ranks were selling information to the News of the World.

Mobile phone companies can provide police with real-time location information about the whereabouts of suspects or missing people at 15-minute intervals. More commonly, police request a "cell site dump", which gives a complete historical record of the whereabouts of person's mobile phone.

There are two ways the data is obtained. When a phone is used for a call or SMS message, details of its location are logged. Alternatively so-called "pinging" can be used when a phone is not in use, by sending the device signals and triangulating the results from cellphone masts. The level of accuracy ranges from a few hundred metres to around two kilometres, depending on proximity to the masts.

Mark Lewis, a solicitor who represents phone-hacking victims, said: "I have sources that I can't reveal who tell me they could do it [obtain the data]." He said he had clients who suspected they had been tracked: "One or two were very suspicious about how they had been found – simply because they were where they were not supposed to be."

If police want to monitor the contents of emails or calls to combat terrorism or serious crime they require a warrant from the home secretary.

Far more common however is the interception of communications data, which relates to the "who, where and when" of messages or calls. There is a complex framework through which the data is channelled from phone companies to police.

Phone companies provide data to "police liaison units" – funded by the Home Office – which contain a handful of people with maximum security clearance to deal with incoming requests.

Police in turn have special points of contact (Spocs), who liaise with the mobile phone companies and process the requests.

They are trained and accredited by the National Policing Improvement Agency and given unique pin numbers. There are almost 600 accredited Spocs in police forces on a nationwide register maintained by the Association of Chief Police Officers.

Under Ripa, these gatekeepers require detailed justifications from a senior officer to request phone information as part of an investigation, in a process that can take up to ten days. In emergencies, senior police can request the information orally, but paperwork is retrospectively filed centrally.

Anyone who suspects their phone was inappropriately tracked is able request details from police or their phone provider under the Data Protection Act.