Siemens Energy boss Christian Bruch defended the €4bn ($.3bn) deal to take full control of Siemens Gamesa as problems piled up at the stricken wind giant.

Shares in Siemens Energy plunged more than 30% in Frankfurt on Friday after it scrapped its profits forecast for the year over a “substantial increase in failure rates of wind turbine components” and other issues at Siemens Gamesa that are now set to dog the business for years to come.