British Gas has denied claims it paid its staff bonuses to inflate customers' bills by up to 60 per cent.
A former employee told the Daily Mail the policy encouraged staff to target charities and small businesses, with workers told they could triple their salary through commission if they sold enough of the most expensive deals as possible.
The whistleblower claimed the energy giant would sign up churches and charities to the highest-priced tariffs in order to boost their own earnings.
"People were desperate to make the salaries they had been promised, so everyone inflated the prices" he told the newspaper.
"Scouts was a favourite one; churches, charities, small businesses, where people would just go for the maximum 5p notch-up."
A British Gas spokeswoman rejected the allegations, saying it regularly reviewed its processes to ensure they were "fair and appropriate".
She said: "British Gas strongly refutes any suggestion that employees are paid commission on any prices charged to residential customers.
"We also reject any suggestion that business contracts have been negotiated inappropriately in our business division, British Gas Business."
She continued: "This is a highly regulated and competitive market, and every part of the sales negotiation process for business customers is closely monitored. The contract is always finalised with the clear and explicit agreement of the customer.
"We take very seriously any concerns raised by employees or customers, and our processes, as well as sales agents' terms, are regularly reviewed to ensure they are fair and appropriate."
