ScottishPower has apologised unreservedly to customers affected by misselling by doorstep and telesales agents.
ScottishPower's chief executive of energy retail and generation, Neil Clitheroe, said he was "happy that this matter has now been concluded".
Mr Clitheroe said in a statement: "I am pleased that Ofgem has made it clear that they found no evidence of a strategy by ScottishPower to deliberately missell to customers.”
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The retailer said there was no elevated risk of fire or explosion and there had been no reported incidents.