The work will be for 10 years and is worth up to £1.5bn.

The Decommissioning Delivery Partnership as it’s called is not a traditional contract but a commercial framework agreement that can be called upon when support is required.

Project Manager Angela Mackintosh said: “Awarding a longer-term 10-year arrangement provides better security of demand for the supply chain, which in turn drives innovation and provides socio-economic benefits through investment in people, technology and infrastructure.

“We want to see positive wider economic benefits to the local community from the enormous amount of public money spent at Sellafield and to get maximum benefit for every pound spent.”

The formal stage of the acquisition process has now begun.

This will be followed by a tendering process at the end of 2014, leading to the announcement of the preferred suppliers in mid 2015.

Chief Decommissioning Officer Jack DeVine said: “To help us complete our clean-up mission, we will put in place a commercial mechanism so that we can very quickly and efficiently pull together specialist resources for decommissioning work to supplement our existing workforce.

“Some 11,000 people work at Sellafield and I have no doubt that there is nowhere else in the world with the same concentration of nuclear experience and skills.

“However, we need external assistance to carry out specialist work that we can’t cover with our own in-house workforce.”