The government must reverse its opposition to new building regulations that ensure homes, hospitals and schools do not overheat as the number of deadly heatwaves rises, according to its official climate change advisers.

The Committee on Climate Change (CCC) recommended the new regulations in 2015 but ministers rejected the advice, citing a commitment to “reduce net regulation on homebuilders”. Without action, the number of people dying as a result of heat is expected to more than triple to 7,000 a year by 2040, the CCC warns in its annual report on the UK’s progress on tackling global warming.

Earlier in June, Britain experienced its longest period with temperatures above 30C since 1976. Heatwaves are known killers in the UK and the number of hot days is rising. On the hottest day of the year in 2016 there were almost 400 extra deaths, while a heatwave in 2006 led to 680 people dying and another in 2003 contributed to the deaths of about 2,000 people.

“What we need from government is a willingness to accept that building regulations, properly done, are not an incubus [problem] – they are in fact an opportunity to enable people to build for the future,” said Lord Deben, chair of the CCC and a former Conservative environment secretary.

“It is absolutely essential to recognise that we will not deal with the problems of climate change unless we have tougher building regulations,” he said. “The government has a real opportunity to do that as it is going to have to look at its building regulations in any case because of the tragic events [of the Grenfell Tower fire] and I think it is very important that they should take the opportunity to look at them in this wider sense.”

The CCC’s head of adaptation, Daniel Johns, said: “We said [in 2015] there is a compelling case for a new building standard to avoid new homes overheating. But [the government] response said there was clearly a trade-off here and they were also mindful of burdens on developers. So this is an area where they consider the potential small additional cost that could be borne by developers and what that might mean for the price of houses, being traded off against the potential long term cost for people occupying these properties in the hotter summers and heatwaves in years to come.”

The CCC identifies hospitals and care homes as particularly vulnerable to heat, as the UK’s ageing population suffers most in hot temperatures, as well as schools and prisons. The best solutions for keeping buildings cool involve good ventilation at night and shading of windows during the day, said Johns.

Air conditioning should not be the first choice, said Deben: “If buildings are properly built in this country there is very little need for air conditioning. The problem with air conditioning is that it heats the area round about, so it has a disadvantage for the community as a whole. It’s a constant pushing out of hot air.”

Julie Hirigoyen, chief executive at the UK Green Building Council, said: “The issue of overheating in buildings is of increasing concern. Clearly, there is a risk that our building regulations are no longer fit for purpose without robust protections against overheating.”

The CCC’s annual progress report says that the UK has done well in tackling climate change, cutting emissions by 42% since 1990 while GDP has risen by 65%. But it warns that the transition to a resilient, low carbon economy is in danger of being “derailed” by delays in important policies caused by the Brexit referendum and recent general election.

“The events of the past year have been, by almost any measure, exceptional,” said Deben. “However, it is now time for government, and for parliament, to act. Climate change is happening, not waiting. It is neither justifiable nor wise to delay further.”

The UK is on track to miss its legally binding targets for cuts in carbon emissions and the plan to address this, expected in late 2016, will not now be published until autumn 2017. Emissions from energy have fallen, although key policies promoting this end in 2020. But emissions from transport and heating are rising and need to be urgently addressed, the CCC said.

Furthermore, the overall state of the UK’s natural environment is worsening, reducing its ability to withstand climate change. The government target is for 50% of land habitats to be in good condition by 2020, but only 25% currently are, crucial pollinator insects are declining and the government has repeatedly missed targets to plant 5,000 hectares of woodland a year.

Progress to tackle river and coastal flooding has been made, the CCC says, but the widespread problem of flash flooding has not been adequately addressed.

A government spokesman said: “The government is a world leader in tackling climate change and committed to meeting the UK’s targets. Our industrial strategy continues to support our burgeoning low carbon sector which is helping deliver high-skilled jobs across the country.”

“We’ve implemented the majority of recommendations from the first National Adaptation Programme report.” he said. “But we agree there is a need to do more.”