OFGEM has launched an investigation into doorstep selling by energy giant E.ON.
The energy watchdog says it has evidence E.ON staff might be using misleading sales patter to lure customers.
E.ON said it was disappointed by the probe because its sales staff acted responsibly and by the rules.
Audrey Gallacher, director of energy at Consumer Focus, said: “Mis-selling has been a consistent problem in the energy market. Any suspicion that a supplier is in breach of their obligations to sell fairly must be tackled head on.
“While it is unclear what types of sales E.ON may be suspected of misleading consumers on, we would hope this announcement will cause them to rethink ending doorstep sales. E.ON has persistently failed to take action on this unwanted sales activity, despite being the only major supplier left selling at people’s homes.”