Thousands of households in North Kesteven were in fuel poverty before the national energy crisis, new figures show.
The End Fuel Poverty Coalition has warned many more will struggle to afford rocketing bills this year after the energy price cap rose in April and the war in Ukraine led to an increase in wholesale oil prices.
Department for Business, Energy and Industrial Strategy figures show 5,959 households in North Kesteven were in fuel poverty in 2020 – the most recent official figures.
This was up from 5,860 the year prior, meaning 12.1% of people lived in a property with an energy efficiency rating of band D or below and, after heating their home, had a residual income below the official poverty line.
Across England, more than 3 million households (13.2%) were in fuel poverty in 2020, the lowest proportion since records began in 2010.
However, these figures do not account for the current explosion in fuel prices, which saw the energy price cap increase by 54% in April, meaning many households can expect to pay around £700 more per year on their bills.
The annual limit on tariffs is due to rise again in October, and Michael Lewis, chief executive of energy company EON UK, warned MPs between 30 and 40% of people in Britain could end up in fuel poverty.
He added that customers' debts could rise by 50%, or around £800 million.
Simone Rossi, chief executive of EDF, also warned parliament that the company had received 40% more calls from customers worried about debt.
Simon Francis, from the End Fuel Poverty Coalition, said the 2020 figures show "just how significant the Government's failure to tackle fuel poverty has been" and estimated more than 6 million households in England have now been thrust into fuel poverty.
"The impact of measures taken pre-pandemic has barely shifted the dial – and we know very little has been done since 2020 to change the picture," added Mr Francis.
"We need urgent help for households in fuel poverty now combined with a long-term plan to improve energy efficiency of our homes and a sustainable, renewable-led, energy mix."
Peter Smith, director of policy and public advocacy at National Energy Action, said the "poorest households are all too often also disproportionately impacted by poor housing" and urged the Government to fulfil its £9.2 billion commitment to improving the energy efficiency of homes, schools and hospitals.
"Improving energy efficiency should be at the forefront of the UK’s response to the energy crisis," added Mr Smith.
A Government spokesperson said it is continuing to make "significant progress on tackling fuel poverty."
They added: "We are investing over £6.6 billion this parliament and working directly with local authorities to further boost energy efficiency in homes across the UK, which remains the best long-term method to keep household energy costs down".