Stricken contractor Carillion agreed a £47.7m sale to Serco in December as part of efforts to reduce its debt.

Since then, Carillion filed for liquidation allowing Serco to negotiate a revised business purchase agreement with liquidators and special managers at PwC and will now be paying £29.7m for the business.

Serco said: “The agreement covers substantially all of the assets that were the subject of the previous agreement.

“The change in consideration reflects Serco’s re-evaluation of potential liabilities, indemnities, warranties and the additional working capital investment required as a result of Carillion’s liquidation.”