No gas boilers have been repaired since April under a government scheme intended to combat fuel poverty, as a result of spending cuts that risk leaving poorer Britons unprotected from the cold at home, according to a fuel poverty pressure group.

National Energy Action (NEA), which obtained the figures from the Department for Business, Energy and Industrial Strategy (BEIS), said the drop in official support via the energy company obligation (ECO) threatens the health of low-income households. Peter Smith, NEA’s director of policy, said: “This leaves thousands of people with existing medical conditions facing a winter without any effective space heating or hot water.”

Consumers fund the ECO through their energy bills, but its annual budget has been cut from £800m to £640m as part of government attempts to reduce bills. The scheme’s spending has been concentrated on replacing a small number of faulty boilers, rather than repairing them.

But the number of replacement boilers being installed through the ECO programme has fallen from a high of 85,000 in 2013 to a low of 7,000 between April and June this year. No gas boilers have been repaired since April.

Temperatures in Britain were expected to drop below freezing on Sunday night as autumn turns to winter, with forecasters predicting that a cold spell could last for several weeks. A scattering of snow was reported in Cumbria on Sunday, the first in the UK this winter, with snowfall expected on higher ground in Scotland on Monday.

Dan Jarvis, the Labour MP for Barnsley Central, said the decline in funding for vulnerable households was causing unnecessary hardship. “Sadly I know all too well this is bound to have very negative consequences in my constituency, causing needless winter deaths and acute suffering.”

The lack of support for repairing and replacing boilers has been raised several times in parliament recently, but NEA accused the government of failing to recognise the severity of the problem. NEA said its research showed engineers and local authorities were making daily contact with people who had had their gas appliances condemned but could not afford to fix them because of a lack of official support.

The charity estimated that over the past four years more than £5bn of public money has been spent treating health problems caused by cold homes. It argues that funds should be spent making vulnerable households warmer and more efficient.

We know the tragic consequences of not being able to afford to service, repair or replace unsafe gas heating appliances Chris Bielby, Gas Safety Trust

At the recent launch of the government’s clean growth strategy, ministers committed to continuing the ECO scheme until 2028. But it is unclear how much funding it will receive.

A spokesman for BEIS defended its policy, saying: “Government action is decreasing the fuel poverty gap and we made a long-term commitment to continue funding the ECO programme at current levels as part of the clean growth strategy.

“We’re replacing boilers rather than repairing them, with 13,000 installed between April and August alone, and funds available for thousands more. Overall, the ECO scheme is on track to upgrade the energy efficiency of well over 200,000 homes in 2017.”

Chris Bielby, the chair of the charity Gas Safety Trust, which aims to prevent carbon monoxide poisoning, shares the NEA’s concerns. “We know the tragic and fatal consequences of not being able to afford to service, repair or replace unsafe gas heating appliances, particularly for the most vulnerable in our society.

“It can put households or nearby neighbours at risk as a result of carbon monoxide poisoning or potentially, in extreme circumstances, cause fires or gas explosions,” Bielby warned.

The problem could inadvertently be exacerbated by the rollout of smart meters, which send readings direct to energy suppliers and are being offered to every home by the end of 2020, NEA said. Engineers fitting the meters are obliged to turn off unsafe gas appliances they find during their visits.

Industry is urging ministers to take action in the autumn budget to help address the lack of funding for vulnerable households to fix their boilers.

Mike Foster, the chief executive of the Energy and Utilities Alliance, which represents boiler manufacturers, said: “The upcoming budget must address this worrying gap in support.”

The interventions came after the energy regulator, Ofgem, warned last month that it was concerned some consumers were rationing their use of gas in response to higher energy prices.