Leighton's biggest shareholder, Hochtief, has made a conditional cash takeover bid for the Australian construction group at $22.15 per share.

Hochtief, which currently owns 58.77 % of Leighton, said today it aims to raise its holding in Leighton to 74.23 % for A$1.155 billion ($1.05 billion) in an off-market offer that requires regulatory approval.

The 75 % limit is significant because it would trigger a change of control in Hochtief's debt covenants.

Hochtief, which is majority owned by Spanish developer Actividades de Construcción y Servicios (ACS), plans to take over a majority of directorships and conduct an extensive efficiency review of Leighton. It also plans to conduct a review which will focus on making Leighton's operating businesses more efficient.

Leighton grew its 2013 full year net profit by 13 % to A$509 million. The company has forecasted 2014 net profit to be from A$540 million to A$620 million, helped by strong mining activity and better margins.

Leighton is engaged in building, civil engineering, construction, contract mining, telecommunications, environmental services, property development and project management in Australia, and in Asia, the Middle East and Africa. The company operates in the infrastructure, resources and property markets. The company also performs offshore work in oil and gas.