Around 90 miles of English coastline should be left to fall into the sea because the small communities there are not worth saving from climate change, government advisers have said.

Small towns along England’s east coast are likely to be abandoned to rising sea levels within the lifetime of the children living there today, said the Committee on Climate Change.

Sea levels could rise by more than 3ft by 2080, which would bring flooding for coastal residents, as well as 1,000 miles of major roads, 400 miles of railway line and 55 legacy landfill sites.

The warning of “tough choices” ahead for coastal communities emerged in a report that shows the cost of keeping the sea at bay will outweigh the benefit of saving small towns or low-grade farmland.

It could cost up to £30 billion to shore up the defences of the 1.2 million homes at risk of being submerged or washed away as sea levels rise.

For some communities the eye-watering price to keep rising waters at bay would not be a government investment worth making, the climate experts said.

“It’s time people woke up to the very real challenges ahead,” said Prof Jim Hall, the committee’s adaptation expert.