Energy supplier SSE has been fined £10.5m by the regulator Ofgem for mis-selling gas and electricity.
The fine is the largest ever imposed on an energy supplier by Ofgem.
In its statement, Ofgem said SSE, formerly known as Scottish and Southern Energy, was guilty of management failures that led to “prolonged and extensive” mis-selling.
SSE said it was “deeply regretful” about the mis-selling, and apologised to its customers.
The mis-selling relates to telephone, in-store and doorstep sales, Ofgem said.
It said customers contacted by SSE were exposed to misleading statements, inaccurate and misleading information on SSE’s charges, and misleading comparisons between SSE’s charges and costs of other suppliers.
Some customers were told they would save money when in fact they were switched onto a more expensive contract.