The company said David Blair, a Laing veteran of 36 years, had retired from the board and his job as chairman of Laing Construction with immediate effect.
Sources close to John Laing said Mr Blair's departure was unexpected, and had been partly due to the problems with the Cardiff stadium, which left the company with a pounds 26m provision. He was on a two-year rolling contract and last year earned a salary of pounds 180,000, putting his potential payout at around pounds 360,000.
The company gave no reasons for Mr Blair's retirement, but his departure is part of an extensive shake-up in the contractor's top management. The company revealed yesterday that Tony Evans, managing director of the civil engineering division and the executive in direct charge of the Cardiff project, had left earlier this week.
The contractor is in the midst of a sweeping restructuring, which would see the merger of its construction, management contracting and civil engineering activities into a new division, Laing Ltd.
Mr Blair, who joined Laing in 1962, will be replaced by Jim Armstrong, the group finance director, who will become chairman of Laing Construction, and Paul Whitemore, who will be the division's chief executive.
A fortnight ago, Laing revealed that cost overruns on several projects, including the Cardiff stadium being built for the Welsh Rugby Union, would wipe away a large chunk of this year's profits. The company blamed a number of last-minute design changes to the original project for the delays.
At the time of the announcement, Laing insisted that the Millennium Stadium would still be completed in time for the inaugural match between Wales and South Africa on 26 June.