Scottish Power will become the first major UK energy company to use only wind power, after selling off its remaining coal and gas stations.

Yorkshire-based power company Drax bought the stations for £702m.

This is a pivotal shift for Scottish Power, who plan to invest £5.2bn over four years to more than double its renewable energy capacity.

Chief Executive Keith Allen said: "Every working day we are investing over £4m to deliver cleaner, smarter power for customers.

"From today we can focus solely on making energy generation cheaper, cutting carbon quicker, building smart grids and connecting customers to renewable electric future for transportation and heating."

Scottish power was acquired by Spanish based Iberdrola in 2007 and over the last decade has closed all of its coal plants.

The chairman and chief executive of Iberdrola, Ignacio Galán said: "Energy companies must be part of the solution to climate change.

"Iberdrola is acting now to cut carbon emissions 30% by 2020 and be carbon neutral by 2050. The sale of these generation assets is consistent with our strategy."