Half a million more people have been plunged into "fuel poverty" due to the rising cost of gas and electricity, but few are benefiting from so-called social tariffs, research shows.

For every one per cent increase in household utility bills, a further 40,000 households are plunged into fuel poverty, according to the Department for Business, Enterprise & Regulatory Reform.

With average bills rising 12.5 per cent following price increases pushed through so far this year - to £1,026 from £912 - a further 500,000 people are now "fuel poor", taking the total to 4.5 million consumers, according to price comparison website uSwitch.com.

However, Britain's big six energy suppliers have signed up fewer than 400,000 people to social tariffs, designed to help those struggling to meet energy costs.

Even if suppliers carry through current plans to widen social tariff provision, they would still only help less than one million customers, uSwitch said.

Meanwhile, the government's winter fuel allowance now covers just 19.5 per cent of a pensioner's annual energy bill, compared to 34.5 per cent four years ago.

Ann Robinson, director of consumer policy at uSwitch.com, said: "If the government is truly committed to breaking the stranglehold of fuel poverty in this country then it needs to work with the industry and regulator".