Neil Wilson, senior market analyst at ETX Capital, said Centrica was heading for a record share price fall, with the stock already down two thirds in the last four years.
Britain's big energy suppliers are under pressure from smaller rivals able to offer cheaper deals.
It's not merely in the United Kingdom the company is struggling - its North American division is suffering "significant downward pressure" on its margins, due to "highly competitive market conditions and low price volatility".
Investec's rating on Centrica is now under review, Patel said.
Britain's biggest energy provider saw the customer exodus following its move to increase electricity prices by 12.5% in September, although it said 150,000 of the accounts lost were exclusively down to market switching trends following the tariff rise.
As of 09:32 GMT, Centrica's share price had given up 16.32 percent to 136.64p, pressuring the benchmark FTSE 100 index which now stands 0.27 percent lower at 7,399.25 points.
Forecast: Warmer weather expected for Thanksgiving
Fog should clear up by 11 a.m. according to the weather service, and isn't anticipated as a problem through the rest of the week. On Thursday , the highs should reach near 71, with mostly sunny conditions and calm winds.
Chief Executive Iain Conn told investors on a call that more details on the dividend policy would be given at Centrica's annual results in February.
Centrica said the full year dividend per share was underpinned, as the firm's net debt was expected to be within its £2.5bn-£3bn range and adjusted operating cash flow for the year will top £2bn. This reflects the impact of a one-off, non-cash charge of 46 million pounds ($61.1 million) in its North America business, Centrica said.
A collective switch with British Gas negotiated by Moneysavingexpert.com ran out in October and the consumer group negotiated a collective switch deal with EDF Energy (EDF.PA).
It left the firm with a total of 13.1 million customer accounts and 7.9 million customers though the losses marked an acceleration in domestic customer churn in recent years.
Home power bills have doubled in Britain over the past decade to an average of about £1,200 a year.
The news follows mere days after Centrica announced it would scrap its controversial standard variable tariff (SVT) for new customers from April 2018, after Prime Minister Theresa May promised to end "rip-off energy prices" by imposing a price cap on SVTs and other default tariffs by 2019. It also called on the government to phase out SVT deals altogether and prohibit so-called evergreen tariffs without an end-date, arguing that such deals reduce customer engagement.