His duties will be taken on by Paul Sheffield, managing director of the group’s Europe Hub.
Wells’ departure was announced to the firm after Ray O’Rourke called a meeting in London of senior directors to review performance across the £4bn turnover group.
A source told the Enquirer: “The word is Ray has been reading the riot act. There are problems with old contracts.”
In September, Laing O’Rourke revealed that difficulties with off-site prefabrication on several UK contracts had plunged its European operation into a £58m pre-tax loss in the year ending April 2015.
And Anna Stewart, group chief executive, warned that 2015/16 would also be tough because of legacy contracts and cost inflation.
Wells is a high level departure, who has been responsible for overseeing UK infrastructure, under Sheffield, including successful bidding for Thames Tideway Tunnel work.
He joined Laing O’Rourke just over two years ago from the Middle Eastern contractor Al Naboodah Construction Group where he was chief executive for two years.
Prior to that he spent five years with South African engineering and construction group Murray and Roberts. Earlier in his career he spent 15 years with the Costain Group in a variety of strategic, operations and project delivery roles.