More than half of homes in Buckinghamshire have poor energy efficiency ratings, figures show, as campaign groups warn of soaring fuel poverty even with the new Prime Minister's energy plan.

Prime Minister Liz Truss announced that energy bills will be frozen at no more than £2,500 a year for all homes in England, Scotland and Wales, as part of a package of support aimed at tackling the cost-of-living crisis.

However, the End Fuel Poverty Coalition campaign group said the new measures would be an "expensive sticking plaster" if they were not accompanied by longer-term investment in energy efficiency and renewables.

Analysis of energy efficiency ratings by the Office of National Statistics shows 56% of houses had a ranking of "D" or below as of March 2021 – the latest figures – meaning they are likely to be worse impacted by the rising cost of fuel.

Energy Performance Certificates show how effective a home is at keeping heat in – with ratings from A (the most efficient) to G – the least, meaning residents have to spend more on energy bills to keep their homes warm.

The End Fuel Poverty Coalition estimates that 6.9 million households across the UK will suffer fuel poverty this winter, even after the new price guarantee – including around 5.3 million households in England.

The latest figures from the Department for Business, Energy and Industrial Strategy estimate there were around 3.2 million English households in fuel poverty in 2020 – including 15,939 in Buckinghamshire.

And separate figures from charity Friends of the Earth show, as of August, 20% of dwellings in Buckinghamshire did not have their lofts insulated, and 19% were without cavity wall insulation – equivalent to 46,500 and 44,300 homes respectively.

Adam Scorer, chief executive of fuel poverty charity National Energy Action, called the PM's announcement "good news", but warned more must done for those most in need.

"The new Government must not forget that the most vulnerable need targeted support," he said.

"Those who use more energy in their homes because of medical conditions, those who are elderly and those on very low incomes need extra help, so they don’t have to ration their usage, putting their physical and mental health at risk."

Sir Keir Starmer, leader of the Labour party, said the plan "does not come cheap" and criticised Ms Truss for funding it through increased Government borrowing, rather than a one-off tax on energy companies.

The Prime Minister said it was a "moment to be bold". “We are facing a global energy crisis and there are no cost-free options,” she said.

Chancellor Kwasi Kwarteng is set to provide more details in an announcement later this month.