An investigation into the customer service, billing and complaints handling processes of Extra Energy has been launched.
Ofgem said it is examining whether the energy company breached its Standards of Conduct, which are aimed at ensuring suppliers treat customers fairly.
It will also look into whether the power firm broke rules regarding meter readings, refunding credit and issuing late final bills.
Ofgem said Citizens Advice raised concerns in March relating to a “high level of complaints” against Extra Energy, particularly around billing while the Ombudsman raised concerns in April relating to the energy firm’s ability to complete remedies within the required timescales.
Last month Citizens Advice revealed there were 1,682 complaints per 100,000 Extra Energy customers between January and March this year – the highest ratio ever recorded over the course of the league table’s five-year history.
However Ofgem added: “The opening of this investigation does not imply that we have made any findings about non-compliance.”
Extra Energy said it has taken the company “longer than we expected to adapt our systems and processes to some of the more specific nuances of the UK market”.
Managing Director of operations Ben Jones added: “We’re working closely with Ofgem to resolve these issues. Many have now been fixed and are a thing of the past, thanks to a programme of improvement work we have had in place since early this year. However, some challenges do remain and we have presented a clear plan to Ofgem detailing how we will fix them within the next three months. We’re confident that we will come out of this stronger than ever and that our customers will benefit.”