While the investigation into the way energy companies sell deals over the phone revealed some great improvements, it found that some companies, including British Gas and Eon, are still struggling to give people the right information.

When mystery shoppers rang up British Gas to get a quote for its cheapest deal, it gave them a range of inconsistent prices.

The energy giant quoted one shopper £72 more than the cost of the deal, while another was given a quote that was £46 cheaper than it should have been. 

Meanwhile, Eon gave one shopper a quote that was £34 more expensive and one that was £50 cheaper than it should have been.

The report also highlighted that the tariffs are so complicated even the sales people of the energy companies had a tough time calculating what the end price for a tariff per year would be.

Richard Lloyd, Which? executive director, said: “It’s good that the information given by energy company salespeople has once again improved, which reflects the work already done to make tariffs simpler, but we’ve found that some are still struggling to provide customers with the correct prices for their cheapest tariffs.

“Our research shows that energy telesales staff can be just as confused by the tariffs and pricing on offer as their customers, which means people have less chance of finding the best deal.

“As it stands the energy market just isn’t working well enough. If consumers are to be confident of getting a fair deal the government must go further with their proposed reforms and require all suppliers to use single unit prices for their tariffs, so that people can spot the cheapest deal at a glance.”

When British Gas was asked about the report’s findings, it said: “We expect our inbound customer services agents to provide a full and comprehensive sales experience that customers can trust.

“While Which?’s research indicates that we may not have got it absolutely right on every call, you have our assurances that we will use your research to drive further process improvements where necessary.”

Eon said: “The quote will be impacted by factors such as payment method, metering type etc and is automatically generated by our system. This information is shown to the customer on their welcome pack. The customer can review this to ensure that the correct information has been used.”