Ofgem investigates 'E' energy supplier
The energy supplier E is to be investigated by the regulator Ofgem for potentially misleading its customers.
The company - which has 100,000 pre-payment meter customers - faces a fine of up to 10% of its turnover.
Under the rules, all energy suppliers are supposed to communicate fairly and transparently with their customers.
The investigation will examine claims made in the company's sales and marketing campaigns. E said it had no comment to make.
Separately, Ofgem said that the number of energy customers in debt had fallen.
In 2015, 1.05 million gas customers fell behind with their bills, compared to 1.2 million the previous year.
Last year, 1.2 million electricity customers were in debt, compared with 1.4 million in 2014.
However, those who are in debt now owe an average of nearly £600 on both their gas and electricity bills, a rise on the previous year.