A furious homeowner blasted British Gas over its "preposterous" £5,000-a-year energy estimate and vowed to battle the eye-watering bill.
Richard White saw his monthly direct debit increase by 115 per cent after it rocketed to £429.41 on August 1, he told KentLive.
Gas prices again spiked again on Monday with one leading consultancy warning that many could be looking at an annual energy bill of almost £5,500 from April.
The latest grim cost of living forecast comes as pressure grows on the Government to add to its £400 help for households with bills that will be paid in six instalments from October.
The 43-year-old from Tunbridge Wells, Kent, wanted to warn other customers to check their bills - especially those who had direct debits set before the government subsidy.
The communications specialist said he complained to British Gas on August 4, and asked the company to justify the increase.
Furious Mr White warned that if the firm did not fully resolve his complaint within eight weeks, he would escalate it to energy regulator Ofgem.
British Gas admitted in writing to Mr White the bill was "quite the jump" and that it had not "factored into this projection" the £400 subsidy from the Government for energy bills.
The customer said: "My partner and I live in a modest three bedroomed detached home with a cat by Toad Rock.
"It is not the base camp for an arctic expedition so for British Gas to predict we are going to burn more than £5,000 worth of energy a year is preposterous., a figure they jovially describe to me in the email as 'quite the jump'."
He said the company must have believed he was "running a gas fired power station in Narnia".
He said British Gas was taking "obscene and disproportionate" amounts from customers as energy prices rose because the war in Ukraine had threatened supplies from Russia.
"In my own little way, I am now punishing British Gas by more than halving the direct debit sum until my credit [or interest-free loan they have taken without my permission, depending how you look at it] is reduced to a level that suits me," he said.
"Everyone who had direct debits set by British Gas before the government subsidy was announced may wish to check to see if this is still accurate.
He said "British Gas accepts it has not taken into account the government £400 subsidy when calculating direct debits. Therefore, it seems all these direct debits have been set too high. It may only be a few pounds a month for some customers, but it is their money and British Gas have done this on a mass scale.
"Simply put, money a family might need to feed the kids, British Gas wants that cash in its back pocket. It's an interest free personal loan from those least able to afford to give one," he said.
A spokesperson for British Gas said: "Mr White's annual bill has not been set at over £5,000.
"We periodically review direct debit payment plans and after reassessing his current plan which ends in October, we advised in his June statement that his payments would rise up until October to ensure his projected usage was covered."
They said Mr White's monthly payment of £429.41 "would not continue for the next 12 months". They also said they were "sorry about the delay in responding" and had explained the adjustment was based on his previous energy use "among other factors".
They said they would also take Mr White's gas and electric meter readings to "bill his account to date".
Households could be facing an annual energy bill of £4,650 from January and £5,456 from April, energy consultancy Auxilione has warned.
This will add nearly £200 to their previous forecast for April, it said.
