The group said that annual greenhouse has emission statistics show that the UK is still failing on climate change and needs to “radically re-imagine” transport.

Transport is a major source of emissions, causing around a third of total pollution. This is mostly caused by passenger cars. New research from Friends of the Earth and think-tank Transport for Quality of Life showed that a 20% reduction in car journeys is necessary to tackle climate change, even with a faster switch to electrics cars and a more rapid decarbonisation of the electricity grid.

Friends of the Earth wants to see a transport system based around people and increased walking and cycling. It pointed out that over 100 cities and towns across the world are reducing air pollution by making bus travel free. It will be necessary to regulate buses to make this work.

Under-30s first

Mike Childs, head of research at Friends of the Earth, said: “It’s an idea whose time has well and truly arrived. Free bus travel for the under 30’s at first, before widening the scheme, would make for more liveable cities and cut damaging greenhouse gas emissions.

“Dozens of cities across the world offer some form of free public transport. It would cost around £3 billion a year but this is a fraction of the money spent on roads. Three times more journeys are by bus than train and they are the main means of transport for the car-less quarter of the population. What we are seeing instead is bus fares rising 75% over the last 15 years, and over 3,300 services reduced or removed since 2010 in England and Wales.”

Lynn Sloman, director of transport for Quality of Life, said: “Transport policy should be evidence-led. Our research makes it clear that UK transport policy requires a complete overhaul to enable us to comply with greenhouse gas reduction needs and other pressing public health concerns such as air quality and obesity.”

Single bus fares in London currently cost £1.50. Passengers can have unlimited travel for £4.50 per day or £848 per year.