Ofgem has ordered Ovo Energy to improve its customer service after it received “serious concerns” over the gas and electricity supplier’s handling of complaints. The energy regulator for Britain said it had told the UK’s third largest gas and electricity supplier to take action after it was alerted to the fact that problems remained unresolved and households faced lengthy waiting times to contact the company. The concerns were raised by Citizens Advice Scotland and the Energy Ombudsman, which works to resolve disputes between suppliers and brokers and their customers. Ofgem said the ombudsman had concerns that Ovo had not implemented remedies the dispute resolution service had suggested in order to improve the company’s complaints handling and that this situation had become “progressively worse over time”. The energy supplier has now been ordered to address all outstanding complaints and cut the amount of time it takes for problems to be tackled and could be fined if the issues are not addressed. An Ofgem spokesperson said: “There are no excuses for poor customer service and Ofgem has made this clear to all suppliers. Where concerns are raised with us, we will follow up and take appropriate steps. “We will monitor the situation and expect to see things improve. However, if they do not we will consider further steps, including the possibility of enforcement action and fines.” A spokesperson for the supplier said: “Ofgem did not identify any non-compliance from Ovo on this matter. We continue to place serious emphasis on the support we provide to our customers and have assured Ofgem of this.” Ovo has grown significantly over the last decade, including through the £500m takeover of SSE’s retail arm in 2019, and now serves 4.5 million customers. This summer, Ovo and rival supplier Good Energy were ordered to pay £4m for overcharging thousands of households on their bills by breaching the government’s energy price cap. Ovo has also apologised to customers who were wrongly billed and admitted errors in dealing with a customer’s meter readings before her death. Last month, the Ovo shareholders Mayfair Equity Partners and Morgan Stanley Investment Management invested an extra £200m, reducing the stake of the energy firm’s billionaire founder, Stephen Fitzpatrick, in the process. A detailed analysis of Fitzpatrick’s ventures by the Guardian in May revealed he had quietly transferred control of Ovo during the energy crisis; had taken a significant hit to his wealth from his flying taxis venture, Vertical Aerospace, and had shut down a project designed to share his business acumen with other companies.