Private contractors are to take over the role of looking after the UK's nuclear weapons in Scotland.

The Ministry of Defence signed a 15-year contract with ABL Alliance on Friday to provide support for the Trident weapons system at the naval base on the river Clyde.

Under the new contract, 149 MoD civilian posts will transfer to the alliance. The jobs are in industrial and technical grades, warehousing and logistic support services, while supervisors and managers are also transferring.

Thirty-nine Royal Navy posts will also be seconded to the alliance, which comprises AWE plc, Babcock and Lockheed Martin UK Strategic Systems.

The MoD said it decided in May 2011 that the most effective way to sustain the workforce in the future was to use an experienced supplier within the private sector.

ABL Alliance will provide support to the Trident strategic weapon system at the Royal Naval armament depot at Coulport and the strategic weapon support building at Faslane.

The MoD said: "HM naval base Clyde has an excellent safety record and we are determined to maintain the highest standards of safety.

"The MoD will continue to own the naval base sites, including Coulport, and naval base commander Clyde will retain overall responsibility for security and for the activities carried out at Coulport and Faslane.

"The site will also continue to be a MoD nuclear authorised site, so will be subject to regulation by the Defence Nuclear Safety Regulator, the Office of Nuclear Regulation and other regulatory bodies."

The new arrangement is scheduled to start in January 2013, subject to the successful completion of a protection of employment consultation.