Shepherd Construction won the preconstruction services contract for the 1960s city centre revamp over a year ago, before much of the business was bought by Wates.
But now a deal has been struck with BAM to deliver the technically challenging refurb for the council which involved adding a 7-storey glazed extension to the front of the office building.
Work on the ten-storey Merrion House, which until recently was occupied by Leeds City Council employees, is scheduled to be finished by the end of 2017.
BAM’s construction director Kelvin Pollard, said: “BAM’s specialist services engineering business will help us deliver what will be a striking transformation.”