Heat-related deaths are set to treble in less than 35 years unless the government takes urgent action to prepare the country for extreme heatwaves, according to the Environmental Audit Committee.
It has warned that the number of vulnerable people, such as the elderly, dying from the heat could rise to 7,000 a year by 2050.
In its report it says ministers need to "stop playing pass the parcel" with local councils and the NHS and take action to ensure homes, hospitals, care homes, offices, cities, water supplies and transport networks can cope with rising temperatures.
More than 2,000 people died in just 10 days in 2003 when a heatwave pushed temperatures to a record high for the UK of 38.5C (101.3F).
The Met Office says that could be topped this week and warns that hot spells of a similar intensity will occur every other year by the 2040s.
Mary Creagh MP, chair of the committee, told Sky News: "I think the government has left the country very unprepared for heatwaves. There's been very little action over the past 10 years.
"What we're recommending in this report is a change to the building regulations so we have more water efficient, less overheating homes, schools and hospitals.
"But also that we take action with our planning framework so that we build greener cities, where people can move, breath, which can cool down at night and give people the relief they need in extreme temperatures.
"As the population ages and becomes more at risk of these types of heat-related illnesses we need to be taking action now and building it in for the future."
The report is published as the UK swelters in a prolonged heatwave hitting northern Europe, with scientists warning that climate change is making such heat extremes more likely.
1:33MPs warned the public do not always take extreme weather alerts seriously and see heatwave warnings as "barbecue alerts".
"The government needs to do a lot more to warn and educate the public about the risks of heatwaves," said Ms Creagh.
"At the moment, heatwaves can only occur between June and September and what we've seen with our more erratic weather patterns is you can get a hot spell in April or in October."
A government spokesperson said the report's findings were being taken seriously.
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"Our long-term plan for climate change adaptation sets out ongoing work and investment to make sure food and water supplies are protected, businesses and communities are properly prepared and the right infrastructure is in place," they said.
"The government will carefully consider each of the report's recommendations."
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