Spending on Operation Rubicon has fallen to a trickle, and, by this summer, only three officers were working on the probe.
Moreover, John McSporran, who was the senior investigating officer on the case, has retired from the force.
In reference to Rubicon, McSporran said on his social media profile: “Retired at the end of this enquiry.”
In 2011, the News of the World was closed following allegations that journalists on the tabloid had hacked mobile phones, in particular the phone of murder victim Milly Dowler.
A multi-faceted investigation by the Metropolitan Police led to the arrests of the paper’s former editor Andy Coulson and one-time News International executive Rebekah Brooks, whose trials are scheduled to begin tomorrow.
Dozens of other journalists south of the Border also face criminal charges. As the News of the World closed, Strathclyde Police launched its own inquiry into whether journalists had broken the law, with up to 50 officers drafted in.
The probe looked at allegations of phone hacking, data protection breaches and possible police corruption.
Detectives also focused on allegations that witnesses in the perjury trial of former MSP Tommy Sheridan had told lies under oath.
During the Leveson inquiry, set up to examine the ethics of the press, the then chief constable of Strathclyde, Stephen House, said he had “no doubt” there were individuals in his force “who are in receipt of money from various people”.
As a result of the investigation, Bob Bird, the former editor of the Scottish edition of the News of the World, was charged with attempting to pervert the course of justice.
Douglas Wight, news editor on the Sunday tabloid, was charged with perjury, conspiring to hack phones, and of multiple counts of conspiracy to obtain personal data.
However, despite an initial flurry of activity, the work of Operation Rubicon now looks to be at an end.
In the first nine months of the probe, an average of £9572 was spent each month on overtime and expenses, while in recent months the expenditure in these areas has struggled to reach £1000. In April, a mere £356 was spent.
According to Police Scotland, which replaced Strathclyde and the other regional forces, the deployment on Rubicon in July was three detective constables and one detective chief inspector, down from the high point of 50.
During his evidence to Leveson, First Minister Alex Salmond gave staunch support to the police probe.
He said: “I’ve asked the Lord Advocate for assurances that the matters which are coming to attention under Operation Rubicon will be properly, thoroughly investigated by a well-resourced investigation, that they’ll go where the evidence leads without fear or favour, and that these matters and the criminal law be upheld in Scotland. I have received these assurances.”
Aamer Anwar, a solicitor who provided police with a dossier on phone hacking, said: “The inquiry is probably at an end, as the evidence has been gathered. What remains is a skeleton staff, who are assisting the Crown Office.”
He added: “I’ve been pleased with the robustness and transparency of the investigating team.”
Scottish Labour’s justice spokesman Graeme Pearson said: “It is important that Operation Rubicon is properly resourced throughout the course of its existence.
Pearson, a former police commander, added: “We can all remember the outrage of the phone-hacking scandal when it first emerged. We can’t now see a drastic reduction of staff and cash until the investigation is resolved.”
Police Scotland declined to comment on the matter, while Scottish Newspaper Society director John McLellan said: “It would be inappropriate to comment on what is still a live criminal investigation.”