Nicola Sturgeon has called for a "sustainable solution to the problem", and said that "Ofgem, the UK Government and energy suppliers need to be held to acc-ount" after 2.2 million households discovered they would face higher energy bills.
The charges will come into play from December 6, and will see gas prices soar by 8.5% and electricity prices rise by 9% on average.
Ms Sturgeon said: "This is another blow to Scottish households, many of which are already struggling to pay their energy bills."
John Robertson MP, who sits on the Westminster energy committee, also slammed the firm, and said: "ScottishPower is treating customers with contempt and totally ripping them off.
"And the fact that they have announced these rises just days before they appear before the committee shows how little respect they have for the Parliamentary process and how confident they feel that this Tory-led Government will let them get away with it."
Iberdrola, their Span-ish parent firm, said it had "no option" but to increase prices, after claiming ScottishPower had been hit by the Government's energy efficiency and environ-mental measures.
ScottishPower is the fourth of the "big six" suppliers to reveal energy price increases this month. Npower raised their prices by 10.4%, British Gas by 9.2%,and SSE by 8.2%.
It comes days after ScottishPower agreed to pay £8.5million after a probe by regulator Ofgem, which uncover-ed misselling by its sales agents.
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