If the official figures are to be believed, the old Strathclyde Police force did a great job in reducing violent crime.

Between 2007 and 2013, serious assaults were down 53.5% and robberies fell by 50.3%.

The force believed a large part of this drop, which happened on the watch of Chief Constable Stephen House, was due partly to stop and searches, of which 612,110 were recorded in Strathclyde in 2012-13 alone, with a success rate of 13.7%.

One research report claimed the total number of searches in this period was over four times greater than stop and frisk in New York City in 2012.

The policy had two aims: to detect drugs, weapons and stolen goods; and to deter people from carrying these items.

When House took the top job at Police Scotland, the Strathclyde model for reducing violent crime was rolled out nationally.

The single force has a "key performance indicator" for the number of stop-searches and a 15% target success rate. In the first nine months of the single force, 519,213 stop-searches were carried out.

However, former police officers say the number of stop-searches by both Police Scotland and Strathclyde is exaggerated. Due to the pressure officers feel, they say some recorded stop-searches are actually invented.

There are two possible outcomes to a stop-search: either "positive", when action will be taken; or negative, when nothing needs to be done. Although an officer should provide full details of all searches in his notebook, more limited details are required when the information is logged electronically. Fields include ethnicity, gender and age - but not the name and address of the person searched.

Former officers have told the Sunday Herald this has led to officers, who feel under pressure to keep the figures high, making up negative searches.

One way of checking a negative search would be to inspect an officer's notebook, which, this newspaper has been told, would be considered a waste of time.

One former officer said: "The public's perception of the police is enhanced when they read that in their particular area 250 people were stopped and searched."

He said some officers simply "make it up", adding: "An hour before I go off duty I could have recorded 12 fictitious stop-searches. No-one would check. It is very easy to cheat the system."

Asked if this practice occurred, another ex-officer responded: "One hundred per cent right." He added that it was not the fault of the officers, but the result of a culture driven by "targets and key performance indicators".

Another police source said he had heard that stop-and-search figures also include double counting, whereby an officer could record details of a legitimate search for drugs, but then file a separate entry for the same person on the grounds that alcohol was also searched for.