Carillion shares plummeted by more than 35pc in early trading as the support services group said its overall performance was expected to be below previous expectations and that it had parted ways with its chief executive.
Carillion said that Richard Howson had stepped down as chief executive after two years in the job, although he is to stay with the company for up to a year to support the transition.
Keith Cochrane has been appointed interim chief executive while the search begins for a permanent successor.
It comes as the FTSE 250 company warned that full-year revenues would be lower than expected amid “difficult” markets and withdrawals from certain territories.
Carillion, which maintains railways, roads and military bases, said it was beginning a “comprehensive review of the business and capital structure”.
It has left the construction markets in Qatar, Saudi Arabia and Egypt, and said it is only undertaking future construction work “on a highly selective basis”.
“Despite making progress against the strategic priorities we set out in our 2016 results announcement in March, average net borrowing has increased above the level we expected, which means that we will no longer be able to meet our target of reducing leverage for the full year,” said Philip Green, non-executive chairman.
“We have therefore concluded that we must take immediate action to accelerate the reduction in average net borrowing and are announcing a comprehensive programme of measures to address that, aimed at generating significant cashflow in the short-term.”
In December, Carillion said the pace of work had slowed in the second half of 2016 partly because of a pause in work from the Government following the vote to leave the EU.