LONDON -- Protesters turned out Saturday on the streets of London and in the Scottish city of Glasgow to demand faster action against climate change following the record-smashing temperatures that scorched the U.K. this week.

Activist groups including Just Stop Oil and Insulate Britain led protesters in a sit-in on Parliament Square in London to demand that the Conservative government stop giving new licenses for oil and gas production, tax big polluters and help people install more energy efficient heating in their homes.

"Tuesday's extreme heatwave was a warning about what we will face as the climate collapses --- thousands of deaths, homes lost to wildfires and emergency services stretched to breaking point," said Indigo Rumbelow from Just Stop Oil. "We are so unprepared for extreme heat and it's only going to get worse."

The U.K.'s Met Office weather agency recorded 40.3 degrees Celsius (104.5 degrees Fahrenheit) in England on Tuesday, the highest-ever temperature registered in a country ill-prepared for such extreme heat. British summers are usually quite moderate and few homes, schools or small businesses have air-conditioning.

The heat wave paralyzed major train networks, damaged airport runways and saw 15 fire departments across the country declaring major incidents. The London Fire Brigade said that Tuesday was the busiest day for firefighters since the Second World War.

In Glasgow, climate activists staged a "die-in" protest to demand urgent action to tackle climate change. Protesters laid on the ground in one of the city's busiest shopping areas, covered in white sheets with "causes of death" including heat stress, famine and water scarcity.

"We've been sounding the alarm about the global climate emergency for years," said Wolf Saanen, 39. "Now it has arrived on our shores, will those with the power to change things finally listen?"

Some climate groups warned they will stage more disruptive demonstrations in the autumn to bring Westminster -- the seat of Parliament -- to a standstill.

The groups also want the British government to reduce energy bills amid a soaring cost-of-living crisis that's expected to squeeze households further in the fall when the weather turns colder.