Sir Peter Mason is to retire from Amec at the age of 60 after 10 years at the helm of the company.
A spokesperson for the company said that he would stay on until after the business had been split into two quoted companies - an international energy and process engineering business and a UK infrastructure and investment business. This is expected by the end of 2006.
He added that no successor for either business had been decided.
Amec has taken a £89m exceptional charge associated with its withdrawal from construction markets in the UK and USA, its oil and gas division, and a legal dispute in the USA.
Pre-tax profit fell 72% to £25m, although profit before the exceptional items were taken into account was up 6.8% to £121m.