Toto Energy will transfer thousands of its customers on prepayment meters to Utilita Energy next month.
The energy supplier said it has been “pushing hard” to improve all aspects of its business and has made the decision for the “good” of customers.
It said the move will ensure customers who are being switched are “well looked after” and will “immediately” make the company better placed to manage resources and service remaining customers “in the way they deserve”.
Toto emailed affected customers over the weekend to notify them about the change, which is expected to take place on 10 April.
But its handling of the transfer has come under criticism from Citizens Advice, which described the company’s communication to customers as “appalling”.
Customers also received an email from Utilita on the same day (25 March), welcoming them to “one of Britain’s fastest growing energy suppliers”.
Victoria MacGregor, director of energy at Citizens Advice, said: “Toto Energy has done an appalling job of communicating this change to its customers.
“We think customers should have been given advance notice of the transfer, giving them the opportunity to decide whether to transfer automatically to Utilita or switch to another supplier.”
She added: “Toto’s customer service in this instance has fallen well below what we would expect of a responsible energy supplier.”
Toto Energy said the company wants to ensure it can always offer customers “the very highest standards of service”.
A spokesperson for the company told Utility Week: “Utilita have been market leading in their service for smart prepayment customers, and for us, as a small company who’ve grown at an incredible rate over the last two years, we want to ensure we can always offer our customers the very highest standards of service.
Ofgem said it will hold both Toto Energy and Utilita to account to ensure customers “do not lose out by being put on a worse tariff or experiencing worse customer service”.
“We are discussing this matter with Toto Energy and Utilita and will hold them to our rules,” a spokesperson for the regulator said.
Utilita Energy, said it will honour Toto Energy customers’ current tariff until at least 30 June.
In its welcome letter to customers, the company’s chief executive, Bill Bullen, said: “As part of a restructure of its business, your current supplier [Toto] has asked us to provide you with the same great level of service we currently give to our 625,000 customers across the UK.
“This means that as of 10 April 2018 Utilita Energy will be your new supplier of gas and electricity.”
The letter also highlighted customers have the right to switch energy supplier.
A spokesperson for Utilita Energy, added: “We are delighted to welcome a number of Toto’s PAYG [pay-as-you-go] customers to Utilita, where they will receive all the great service that has made us Britain’s leading smart PAYG provider – with nearly 90 per cent of our customers installed with a smart meter – and a Which? Top 5 supplier for customer satisfaction.”