Smaller and newer energy suppliers have again rated the worst for customer service in a ranking based on complaints to Citizens Advice.

Toto Energy fell to the bottom of the quarterly ranking by the consumer charity with a score of just 1.45 for the period between April and June, beating only Iresa Energy, which ceased trading in August, in the previous quarter.

Solarplicity, which has appeared in the table for the first time, came second to bottom with a score of 1.8.

So Energy topped the table for the third successive quarter with a impressive score of 4.7, closely followed by Bulb and Octopus Energy.

Citizens Advice said problems reported by Toto Energy customers included not being able to contact the company and issues with billing, with one person complaining that their direct debit was increased by more than £100 and another saying they had been unable to reach the company to resolve their issue for over two weeks.

Toto Energy’s customers spent an average of 23 minutes on hold, and more than one in 10 waited more than a year for an accurate bill, the charity’s figures show.

Citizens Advice said the poor performance of some smaller energy companies and newer market entrants demonstrated the need for tighter regulation.

Ofgem will shortly consult on new proposals for granting licences to energy suppliers as well as the monitoring they should face after entering the market.

Citizens Advice has called on Ofgem to tighten up the rules around who is able to supply energy, saying companies are entering the market before they are ready to deliver adequate customer service and are damaging trust in the market.

Citizens Advice chief executive Gillian Guy said: “Too many customers are being let down by firms which aren’t ready or capable of providing a decent level of service. These aren’t small problems.

“Billing errors, blocking people from switching, and poor communications can cost customers money and make people’s lives a misery.

“Smaller companies at the top of the table show that size is no excuse for poor customer service.

“It’s vital that Ofgem now tackles the problem of newer and smaller firms letting people down and tightens up the rules around who can become an energy supplier.”

A Solarplicity spokeswoman said: “The ratings from Citizens Advice only present a snapshot of the communications in the three months from April to June 2018, and in the last three months alone we have already begun to see significant changes as a result of the measures we have put in place.

“Since July our customer service performance has improved dramatically, with call waiting times cut to less than 30 seconds, better than 90% of all the calls answered, and cases reported to Citizens Advice halved.”