Under the £4.2bn contract, Cavendish will plan to decommission 10 of the UK’s first nuclear power stations, and take over the two research facilities including Magnox and Research Sites Restoration (RSRL), saving more than £1.5bn to UK tax payers.

Cavendish Fluor Partnership is a joint venture between Cavendish Nuclear, which is a wholly owned subsidiary of Babcock International Group, and Fluor.

The shares in the two Site Licence Companies (SLCs) will be owned by Cavendish for 14-year contract period while the SLCs will continue to operate the sites on behalf of the NDA.

Department of Energy & Climate Change State Parliamentary Under Secretary Baroness Verma said: "Today marks an important milestone in the long term environmental restoration programme for the first generation of nuclear sites in the UK."

NDA chief executive John Clarke said: "By introducing a fundamentally different contract, based upon a clear understanding of the scope of work to be delivered across 12 sites over 14 years, we have been able to generate real competitive tension during the competition process."