A winner for the 15-year framework is expected to be announced by the end of the year with the shortlist understood to be now down to a straight race between Balfour Beatty and Morgan Sindall.

Balfour will be desperate to win the deal after losing out to Laing O’Rourke this summer on the £2bn main civils contract to build a new nuclear power station at Hinkley Point C in Somerset.

And Morgan Sindall has shown its desire to win the Sellafield job by setting-up a permanent base in Cumbria after the nuclear client said it was keen to award work to local firms.