An internal investigation is underway at npower after it closed down a sales team in London, following allegations in a national newspaper.
Other members of staff have now been given a reminder about how they should go about their jobs, while calls have been made to put a stop to cold-calling customers on their doorsteps.
A spokesman for npower, which has its head office at Oak House, Bridgwater Road, Warndon, said the investigation was being carried out by employees not connected to the sales department but said she did not know how long it would take.
Mid-Worcestershire MP Peter Luff, who is chairman of the Commons business and enterprise committee, said he was "shocked" about the claims and added he is worried about whether there is a wider problem not only in npower but the industry.
"The question in my mind is how could the Sunday Times journalist get placed with the only team in npower not doing their job properly?
"Are there other people who are working in the same way?"
Mr Luff said npower had taken all of the right steps in response to the allegations but urged the company to look at its working practices across the country.
He said energy regulator Ofgem as well as his own committee would now look at the case.