The UK's biggest single crackdown on rogue security companies has been staged amid evidence that private Glasgow-based firms with links to criminality are spreading their base of operations throughout Scotland.

The Security Industry Authority (SIA) and Strathclyde and Lothian and Borders police forces have raided 140 sites across the central belt, arresting or reporting dozens of guards.

The operation this week, which included swoops on the sites of high-profile, publicly funded work on the M74 extension and Commonwealth Games sites, will give both the police and the SIA a wealth of evidence to use in targeting firms that are controlled behind the scenes by major gangland figures.

Almost 50 offences, including suspected immigration crimes and benefit fraud, were uncovered. The crackdown comes amid calls for a tightening of the Security Industry Act in Scotland to relieve frontline contractors of the burden of dealing with security firms on big public projects by putting the vetting process into the hands of third parties, such as councils.

As part of "Operation Raptor" - to which The Herald was granted exclusive access - Strathclyde officers and their partners checked 75 construction sites and 90 guards across the force area. Some 11 individuals were reported by the police for offences under the Private Security Industry Act 2001, six for immigration offences and 15 for "benefit irregularities".

Across its force area, Lothian and Borders visited 65 sites during "Operation Secure" and detected 17 offences, the majority of which related to personnel working without the appropriate licence.

Detective Inspector Calum Young of Maryhill CID, and one of the lead Strathclyde officers in the operation, said: "I am pleased with the results of Wednesday's operation. The sole purpose of this and the operations that will follow is to target those individuals and companies that continue to act outside the law."

Four years ago, the then president of the Association of Scottish Police Superintendents, Tom Buchan, named several "rogue" private security firms he said had links to criminal gangs involved in drug dealing, extortion and money laundering.

Mr Buchan, who was also chief superintendent of Strathclyde Police, named three west of Scotland firms he said had links to "big-time criminals".

In recent years, several forces have introduced units to tackle vandalism, fire-raising and violence between security firms, but police and the SIA now believe the problem has escalated.

A Lothian and Borders Police spokesman said: "While these raids included an enforcement element, they were primarily carried out to gather intelligence on private security companies.

"There is intelligence to suggest that some private security firms have links to serious and organised crime groups, who attempt to legitimise their activities through the ownership of such companies.

"It should never be forgotten, however, that these criminal networks are responsible for blighting local communities with drugs and violence, and we will continue to ensure that their activities are disrupted.

"Rest assured that any criminality uncovered as a result of this operation will result in those responsible being brought to justice."