For not adhering to the selling standards and selling household gas and electricity contracts in an inappropriate way, United States' four largest power producers could be imposed with heavy fines.

The four big power suppliers: EDF Energy, npower, ScottishPower and Scottish and Southern Energy are under the investigation by Ofgem, an industry regulator agency. They have been found conducting competition restricting activities such as telephone and door-to-door selling, for which a number of people lodged complaints against them.

The steps were taken by the power generators after they failed to strike economical deal over the sale of contracts.

The regulator provided no details on the proofs collected by it against the four accusers. One of its spokesman said, "We had previously found enough serious failings to introduce tougher conditions on the suppliers. We are determined to stamp out mis-selling".

It has been expected that the amount of penalties can be as high as 10% of the total yearly revenues of the Companies.

As per the new rules, before striking any fresh deal, the salesman must provide an estimated amount of before and after costs. Also, the power suppliers must check their activities of door to door and telephonic mis-selling.

The victims of the mis-selling can lodge their complaints by calling at the Consumer Direct hotline.