The regulator said "misleading and unsubstantiated statements" were made to potential customers about prices and savings that could be made by switching to the energy provider.
Failures were found at every stage of the sales process from the opening lines on the doorstep, over the phone, to the confirmation process which follows a sale.
Ofgem also found that SSE management failures led to prolonged and extensive misselling.
We speak to one of those who was actually doing the selling. He left the job because he found he had to 'take advantage of a human being.'
A guide to some of the options open to you as a consumer if you believe you have been mis-sold to by SSE or any other energy company.
Ofgem's £10.5m fine imposed on SSE is the biggest ever authorities have imposed on an energy supplier.