A former News of the World journalist's allegation the newspaper paid police to track mobile phones raises serious questions about the UK's eavesdropping laws, according to experts.
Sean Hoare said it was possible to "ping" a handset's location for £300.
While there is no firm evidence to support the accusation, if true it would undermine safeguards within the Regulation of Investigatory Powers Act.
The law outlines a system of checks intended to prevent it being abused.
Police can ask mobile networks to determine the location of a phone, based on information from nearby radio masts.
Only a handful of officers in each force is authorised to make such enquiries, and their requests are supposed to be approved by a senior colleague.
The system is regulated and audited by the Interception of Communications Commissioner, Sir Paul Kennedy.
In his most recent report, Sir Paul found in 10% of cases where law enforcement bodies sought communications information, there was poor compliance with the rules.
Such audits are based on a sampling of police requests - something that leaves the system open to abuse, according to solicitor advocate Simon McKay, author of Covert Policing: Law and Practice.
"The resources of the commissioner empowered by statute to review it are fairly restrictive, so circumstances dictate that a tiny proportion of authorisations obtained will ever be reviewed meaningfully or critically by the commissioner," he told BBC News.
Mr McKay added he would not be surprised if leaks had been made in return for cash.
"You are generally dealing with people that are experienced in using and deploying covert policing techniques and therefore their tradecraft equips them particularly well to minimise the risk of detection," he said.
A new law, currently being considered by parliament - the Protection of Freedoms Bill - would require judicial approval for some Regulation of Investigatory Powers Act (RIPA) disclosures, but not those requested by police.
The BBC approached the government to see if it planned to ask Sir Paul to re-examine the safeguards around police use of RIPA.
A Home Office spokesman said it would not be taking such action before the prime minister had outlined the terms of reference for his two enquiries into the phone-hacking scandal.
Daniel Hamilton, the director of campaign group Big Brother Watch, said he was happy to wait, provided there was eventually a review.
"I would have preferred if action had been taken earlier and intercepts had not been used on such a wide basis, but I think it makes sense now an inquiry has been set up and we have received assurances from the PM and the police that there will be a thorough investigation.
"I hope at the end it will be an opportune time to revisit these processes," he said.