Four of the UK’s big six energy suppliers are facing an Ofgem investigation into their sales techniques after concerns were raised about the possibility of misselling to customers, the BBC has reported.

The four companies under to be investigated are Npower, ScottishPower, Scottish & Southern Energy and EDF Energy and all are to be questioned over telephone sales and face-to-face sales of energy contracts.

Ofgem has received information from a variety of sources suggesting they could have breached new rules. All four companies have confirmed they will work with Ofgem on the investigation.

The investigation focuses on the domestic energy market, but business electricity customers should also be wary of cold calling and hard sell tactics from energy suppliers when contracts are up for renewal.

Julian Morgan of Energy Advice Line said: “At Energy Advice Line we do not agree with door step and cold call sales tactics that are being criticised today.”

He added: “We are totally transparent, which is why you can get a quote online. We compare all suppliers to help find the best contract options for your business electricity needs.”

Research conducted by OfGem in 2008 found that domestic electricity customers who switched supplier, more than half did so after contact with a salesman. But many then found themselves on a higher tariff than they were on originally and as a result new regulations were brought in at the end of 2009.

For help switching business electricity supplier, contact Energy Advice Line.

Read the full story at the BBC.