Kier's chief operating officer (COO), Claudio Veritiero, has left the business with immediate effect, after only being appointed in August 2018.
His responsibilities are expected to be split between CEO Andrew Davies and Kier's chief financial officer, Simon Kesterton.
The news follows Kier's chairman Phil Cox stepping down - a role it is yet to fill - after the firm's £245m loss in late September.
Kier is in the middle of a major restructuring programme but has been hit with a fall in the share price and city speculation that it is over leveraged. There are reports it is a target for a possible US private equity takeover.
Under its plans, Kier aims to cut 1,200 jobs by 30 June 2020 and achieve annual cost savings of at least £55m in the financial year ending 30 June 2021. It is also selling off parts of the business with the sale of its housebuilding arm Kier Living 'continuing to progress' it said.
The firm, which has a successful highways division it intends to keep, has said that it continues to be successful in contract work in line with expectations. It has pointed to £1bn worth of new contracts awarded since the end of its last financial year in June.
