Fed-up British Gas customers are deserting the energy giant at the rate of almost 7,000 a day.
A total of 823,000 out of 13.1 million ditched the firm for rivals between June 30 and the end of October.
It means the country’s biggest supplier has suffered a 1.2 million exodus since February.
Owner Centrica claimed most lost customers were on less profitable fixed-price deals.
But it admitted others deserted after it hiked electricity prices by an inflation-busting 12.5% in September.
However, it still expected British Gas to rake in around £810million profit in the 12 months to February – around the same as the year before.
Centrica boss Iain Conn, 55, whose pay and perks rocketed 37% to more than £4million last year, admitted performance had been “disappointing”.
But he insisted he was encouraged by plans to overhaul the firm, including slashing more than 1,500 jobs this year.
Mark Todd, co-founder of the website Energyhelpline, called the customer exodus “terrible news” for British Gas and added: “It shows that the shocking 12.5% electricity price hike has not gone unnoticed.”
John Musk, at investment bank RBC Capital, called the customer losses “eye watering”. Centrica shares crashed more than 15% today – wiping £1.4billion off its stock market value – after it warned profits in North American businesses would be down sharply.
It also revealed a £46million hit from an accounting error.
The firm’s gloomy news comes as British Gas faces being hammered by Government proposals to cap “rip-off” standard variable tariffs which last year accounted for 70% of residential profits.
This week it announced measures to try to avert the move, including phasing out the tariffs for new customers by next April.