More than 800,000 customers have turned their back on British Gas parent Centrica since June, the company said on Thursday, putting shares on track for what analysts are predicting to be their worst day in history.
The customer exodus follows a 12.5 per cent increase in prices in September.
In a trading statement released on Thursday, Centrica said it lost 823,000 customers between June and October.
After the announcement, shares in the firm plummeted more than 17 per cent, down to 135p a share. At the close of trade, shares were down 15.5 per cent, making it the company's biggest ever one-day fall.
Full-year adjusted earnings per share are expected to be around 12.5p. The company put this down to a one-off cash charge from its North America business and warmer-than-expected weather in October and November.
Despite “highly competitive” trading conditions, Centrica said it remains on track to achieve its targets for this year.
The energy giant said it expects its full-year adjusted operating profit for 2017 to be broadly in line with the previous year following a £750m “cost efficiency programme”.
The North America business is expected to report an adjusted operating profit of around £80m, down from £221m last year.
Iain Conn, Centrica chief executive, said: “Although some aspects of our delivery in the second half of 2017 have been disappointing, I remain encouraged by our progress in implementing our strategy.
“The balance sheet has been materially strengthened, and we continue to focus on improving our underlying performance. We have also provided a broad and definitive set of proposals this week to improve the UK energy market for customers and look forward to engaging with the Government and regulator in the coming weeks.”
Centrica said it lost 150,000 customers after they switched to rival firms following the price hike.
A further 650,000 customers left as a result of collective switching, where groups of households club together to negotiate a cheaper deal.
There was also a fall in the number of customers using pre-payment meters and its Sainsbury’s energy tariff.
Earlier this week, Centrica said it was scrapping its variable tariff as part of a package of actions to help reform the UK energy market.
Standard variable rate tariffs are the default price plans offered by energy companies and are typically the most expensive.
Customers attracted by cheap year-long fixed tariffs end up being moved on to the pricier standard variable rate once their deal ends, unless they switch providers.
Energy bills in Britain have reportedly doubled in the past decade, going up by around £1,200.
Last month, Theresa May pledged to introduce legislation to end “rip-off” energy prices by putting a price cap on bills.
Neil Wilson, senior market analyst at ETX Capital, said: “The price hike in September clearly had an impact. You have to wonder why Centrica rushed out its plans to reform the energy market – perhaps it’s seeing a larger number of account losses than planned.”
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