Documents from the Business Department show how the Energy Company Obligation (ECO), which uses funds raised from surcharges on energy bills to pay for efficiency measures such as insulation in fuel-poor households, could also see 20,000 homes receive new central heating systems with gas boilers.

Homes account for around 14 per cent of the UK’s climate pollution. The vast majority of homes get their heating and hot water from fossil fuel-based boilers which contribute to carbon emissions. Cutting emissions from heating is a key part of the UK’s efforts to decarbonise in line its Paris Agreement commitments.

Experts also warn that gas boilers expose families to air pollution. With gas prices on the rise, they could also lock households into a much more expensive option than heat pumps over their lifetimes.

“While it’s important that vulnerable households are supported in staying warm at home, installing new fossil fuel boilers – which contribute to harmful...