British Gas has denied claims it paid its staff bonuses to inflate customers' bills.
According to the Daily Mail, a former employee said 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.
A British Gas spokeswoman said: "British Gas strongly refutes any suggestion that employees are paid commission on any prices charged to residential customers. This is a highly regulated and competitive market, every part of the sales negotiation process for business customers is closely monitored.
"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."