The number of police officers in the UK investigating claims of illegal newsgathering by Rupert Murdoch's media empire has surged past 120.

Strathclyde Police has dedicated more than 50 officers to Operation Rubicon, its investigation into allegations of perjury involving former News of the World editor Andy Coulson and wider claims of phone hacking aimed at public figures in Scotland.

Up to 60 officers are already involved in the Metropolitan Police's Operation Weeting. Scotland Yard also has over a dozen officers working on Operation Elveden, the investigation into allegations of corrupt payments to police officers, and Operation Tuleta, a separate investigation into claims of computer hacking by private detectives hired by News International.

But the decision by senior officers in Scotland to massively boost their investigation into the phone-hacking scandal is a further blow to Mr Murdoch's News International, suggesting that police believe they may have large numbers of potential victims to approach and need to devote considerable resources to the examination of evidence given by NOTW executives during the perjury trial of disgraced politician Tommy Sheridan.

From a small number of officers a few months ago, Operation Rubicon, led by Detective Superintendent John McSporran, now involves more than 50 and has been passed by Scotland the dossier of evidence seized from private detective Glenn Mulcaire.

The surge in manpower potentially reflects the political pressure now being put on the police investigating the NOTW's alleged illegal activities.

Last week, Stephen House, Chief Constable of Strathclyde, confirmed in an email to staff that he had applied to become the Met Commissioner, Britain's most senior police officer.

Six months into the main Met investigation, which began earlier this year, only 170 victims had been contacted by police out of the thousands of names contained in material seized in 2006 from the home in south London of Mr Mulcaire. Rubicon's inquiries are focused on a dossier containing 1,027 names, given to the police by the solicitor Aamer Anwar, who represented Mr Sheridan, the former Scottish Socialist Party leader who was jailed for perjury in a case involving the NOTW's Scottish edition. Mr Anwar said: "This inquiry [Operation Rubicon] has been given massive resources and is looking at allegations of phone hacking, perjury and breaches of data protection. It is an inquiry that will take months if not longer. And the question to be answered is when and who will face prosecution for these crimes committed in Scotland."