British Gas – which trades as Scottish Gas north of the Border – has hiked prices by 3.8 per cent.
The rise is the second this year and will see gas costs rise by an average of £44 per household a year – taking the average bill to £1,205.
The latest increase, which will affect dual fuel customers on a Standard Variable Tariff (SVT), comes after the company announced in April that it was increasing its prices by an average 5.5 per cent from the end of May for both its SVT and its new Temporary Tariff fixed-rate deal, which replaced the standard tariff at the end of March.
The last time British Gas issued more than one price increase in a single year was 2010.
The company blamed the latest increase on a 20 per cent rise in the costs of buying wholesale energy since April.
Consumer groups urged customers to switch energy supplier in an attempt to find a better deal.
Alex Neill, Which? managing director of home products and services, said: “This second price rise within the space of a few months will be infuriating for customers who have now seen their bills hiked by an average of £104 in six months. They should take the power back into their own hands and radically change how much they pay, simply by choosing a better deal.”
Some consumer groups warned that the increase could see customers leave the firm amid more choice in the market.
Mubina Pirmohamed, energy expert at Compare the Market, said: “While wholesale costs are undeniably going up, two hikes in five months is not going to win British Gas any fans. Indeed, having lost 340,000 customers in the first six months of this year, another customer exodus would not be a huge surprise.”
The increase comes a day after the energy regulator increased its price cap on variable tariffs due to rising wholesale prices. Ofgem said its safeguard tariff, which protects five million households from overcharging, will rise by £47 per year in October to £1,136.
Mark Hodges, chief executive of Centrica Consumer, said: “We understand any price increase adds extra pressure on customers’ household bills. However, this reflects the sharp rise in wholesale energy costs. In response to rapidly rising wholesale market costs, since April a number of other energy supply companies have increased their SVT prices and Ofgem have also announced a second increase to the prepayment meter cap.”
Rik Smith, uSwitch.com energy expert, said: “British Gas’s standard tariff was already one of the most expensive tariffs on the market”