The hike will affect around 96,000 customers on Co-op’s Green Pioneer deal and will kick in from 1 April.

It follows recent price increases by EDF and Npower.

The increase represents an average annual £58 jump in the price of energy and gas and follows a £32 hike in energy prices in October.

The firm blamed rising costs for the increase. A spokesperson said: “We try to protect customers from price fluctuations wherever possible. In recent months, however, we have absorbed a number of rising costs, including network charges and industry obligations.

“This is no longer sustainable and we have reluctantly taken the decision to pass on some of these costs to customers by increasing the Green Pioneer standard variable tariff by an average of 5%.”

Responding to today’s announcement, Alex Neill, managing director of home and legal services at Which?, said: “Co-op Energy’s price rise is another blow for customers, who will be outraged that their energy bills are set to go up when the regulator suggested that inflation busting rises are unnecessary. Customers sitting on their standard tariff should look to switch to better deals now.

“Millions of hard-pressed energy bill payers are continuing to suffer due to a lack of competition in this market. If energy companies fail to properly engage with their customers, then the government and the regulator must step in.”

See YourMoney.com’s A guide to switching energy provider to see how you could save money on your bills.