In addition the report says customer money was used to prop up ailing firms with evidence a number of firms were reliant on customer credit balances to provide working capital.
Some of those who contacted Citizens Advice after their supplier had failed told the charity they had average credit balances of £353 with some even reporting their supplier holding over £1000 of their money.
According to Ofgem a typical bill payer only needs to be £150 in credit to cover winter usage.
Chief Executive of Citizens Advice, Dame Clare Moriarty said: “Energy customers are facing a multi-billion pound bill, in large part because Ofgem missed multiple opportunities to regulate the market and tackle rule breaking by suppliers.
“Recent wholesale price rises would have been hard to handle in any circumstances, but they need not have led to the collapse of a third of companies in the market.
“It’s now clear that reform is needed – and this isn’t just about avoiding another crisis.”