Widow Ellen Simpson was surprised when an energy company said her husband had signed a new contract - because he died almost two years ago.

As npower began an investigation, the energy consumer watchdog said the case marked a new low in sales techniques.

Her son, James, said: "This wasn't a mistake. They've cooked their goose this time."

Mrs Simpson, 79, was surprised when she received a letter addressed to her late husband David last week.

But she could not believe her eyes when she read the note thanking him for signing up with the supplier on July 9.

The pensioner, who lives in Eastbourne, also received a call from an npower representative asking to speak to Mr Simpson.

James, from Bexhill, said: "The man told her my father had agreed to enter into a contract with npower.

"She asked for the date when he had agreed to it because she thought it might have been before he died in September 2000.

"But it's impossible. My mother is upset about it for obvious reasons and she knew nothing about a contract. She certainly didn't sign anything."

James is so incensed he has made a complaint to Energywatch, the customer watchdog for energy companies.

He said: "My mother is an elderly lady and this has upset her. As I said to Energywatch, how can you transfer to another energy company without a signature or did someone forge a signature?"

Jennifer Corby, spokeswoman for npower, said: "We are investigating the matter thoroughly.

"We have arranged to ensure that the account is not switched. We will make sure the appropriate disciplinary action is taken."

She was unable to confirm whether a signature was on the contract as npower operates within data protection guidelines.

A spokesman for Energywatch said: "This is an industry-wide problem.

"You think you've reached the bottom of the barrel that the energy companies could go to but there is always something more lurid and more despicable."

A Stop Now campaign was launched in January to stop energy companies selling door-to-door and was backed by 150 MPs.