Energy supplier ScottishPower has defended itself after anger at the firm for putting up energy tariffs when their profits doubled in 2012.

The Scottish provider saw operating profits go from £399m in 2011 to £835m, notching up net profits of £646million and a payment of £890million to its parent company Iberdrola in 2012.

The figures emerged this week after it submitted financial information to Companies House for the last year.

The group Fuel Poverty Action was outraged by the idea Big Six energy firms are “making a killing from profiteering price hikes”.

Elizabeth Ziga from the campaign group said: ‘While thousands of their customers were forced to turn off the heating last winter due to soaring prices, Scottish Power were raking in bumper profits.”

She claimed “hard-pressed UK households have had enough” of an energy system that puts profits ahead of the right to a warm home.

However the energy supplier said its profits only appeared to rise so sharply because they had to write down the value of their Longannet carbon capture and storage project in 2011 by £169million after it was cancelled. In 2012 their profits were given an extra lift, they claimed, because £64m worth of profits from the renewables business were included for the first time.

The firm added it had invested almost £1billion (£957million) in its UK assets in 2012, more than its net profit of £646million.