The Government has faced widespread calls to invest in insulating homes and shifting from fossil fuels to renewables to combat soaring energy prices.

Rishi Sunak has been forced to unveil emergency measures to counter the cost-of-living crisis, including £400 off energy bills for millions of households, but was accused of having “missed the memo” on energy efficiency.

Fuel poverty and green campaigners and politicians called on the Government to invest in home insulation, efficient electric heat pumps and renewables to cut the reliance on fossil fuels whose costs have soared.

Many welcomed the new support for households – and the £5 billion windfall tax on oil and gas company profits also announced by the Chancellor – but said money should have gone into a widespread programme to make homes cosier and cheaper to run.

Simon Francis, co-ordinator for the End Fuel Poverty Coalition, said energy bills will have increased by £1,500 in a year by October, so while the Chancellor’s announcements will take the sting out of the tail of recent price rises, it does not address the underlying problem of fuel poverty.

He said: “People in fuel poverty will need further reassurance that support will be there in the medium term and we need full investment in a ‘great homes upgrade’ to improve the energy efficiency of homes as a national priority.

“Long term, the only way to take people out of fuel poverty is to ensure that their homes are easy and cheap to keep warm. One of the major factors that will help this is investment in energy efficiency measures.

“But people just do not have the savings to spend on making these sometimes costly improvements. This is where the Government could do much more, much quicker.”

Green Party deputy leader Amelia Womak said: “What this Conservative Government still does not understand is that the cheapest bill is the one you don’t have to pay.

“Rishi Sunak seems to have completely missed the memo about the energy crisis and the need for energy efficiency.

“He should be using the money raised from fossil fuel companies to fund the evolution towards a low-energy and renewable-energy future.

“The massive profits made by the fossil companies could be used to insulate our leaky homes and to invest in renewables so that we are resilient in the face of future energy shocks.”

Ed Matthew, campaign director at independent climate change think tank E3G, said the UK has the worst insulated homes in western Europe, and the Government could halve household energy demand by improving energy efficiency – but had to provide financial support for it.

“The windfall tax should have been used in part to do that. It’s a missed opportunity and keeps citizens reliant on gas. We will all pay the price for this missed opportunity,” he said.

And Friends of the Earth climate campaigner, Sana Yusuf, said: “A tax on the excess profits of the oil and gas industry is absolutely the right move, but these measures are a sticking plaster solution that fails to tackle one of the root causes of soaring heating costs – the UK’s poorly insulated homes.

“While emergency support will bring some relief to those already struggling to pay their energy bills, the package misses the opportunity to invest in a free, street-by-street insulation programme, targeting those most in need first, which would reduce bills this winter and in the future.”

Conservative backbencher Chris Skidmore, chairman of the all-party parliamentary group on the environment, welcomed the windfall tax on oil and gas companies.

He added: “Moving forward, we should look at a new multi-annual net zero fund to help get off volatile gas, support renewables, insulate homes, and keep energy bills down permanently.”

Poorly insulated homes use more energy to heat, racking up bills compared to efficient buildings, while gas and oil heating have become more expensive as the cost of fossil fuels soar in the face of higher global demand and efforts to curb reliance on Russian resources.