EDF Energy has become the latest “big six” supplier to hit customers with a hike in gas and electricity bills as it revealed tariffs will rise by 3.9% in January, as the Government warns that energy customers should not be seen as “cash cows”.

The French-owned group claimed it was “holding back” the full impact of rising charges to limit the increase for its 3.7million residential customers.

The tariff rise - which will come into effect on January 3 - means its average annual standard variable rate bill will increase by around £49 a year to £1,300.

The announcement came as a Government minister prepared to issue a warning that energy customers should not be seen as cash cows, to be “squeezed” in the pursuit of a higher return for shareholders.

Energy Secretary Ed Davey will tell Energy UK’s annual conference that trust between firms and customers was breaking down, amid continued controversy over soaring bills.

Power companies have to make profits so they could invest in energy infrastructure, secure supplies and develop more energy efficient technologies, as well as create jobs, he will tell the London conference, adding: “But those profits cannot come at the expense of the elderly, the vulnerable, and the poorest in our society. Customers are not just cash cows to be squeezed in the pursuit of a higher return for shareholders.

“Trust between those who supply energy and those who use it is breaking down. It is so difficult for people to work out what exactly they are paying for that they fear the big energy companies are taking them for a ride when bills go up.

“Fair or not, they look at the big suppliers and they see a reflection of the greed that consumed the banks. So this is a ‘Fred the shred’ moment for the industry. You deliver an essential public service, so your industry must serve the public - and the public must have trust in what you do.”

The minister will say the Government is looking at how it could reduce the impact of its policies on bills.

“But our commitment must be matched by a commitment in industry to open up your books and set out exactly how you are bearing down on your own costs to make bills as low as possible.

“The industry must be much more transparent and Ofgem will have our full support to introduce whatever regulations are necessary to deliver that greater transparency.”

A spokesman for Energy UK said: “The energy industry is already working hard to ensure everyone can keep the lights on and stay warm this winter. The best way to do this is for everyone to work together, which is why this tit-for-tat Punch and Judy show of insults is so unproductive.

“The energy industry is vital to the UK. It is a major employer, a serious investor and a significant taxpayer. As analysis from UBS shows, about 95% of rising energy costs are out of the hands of the energy companies and can be attributed to Government policies and other network, social and environmental costs.”