Families should have no more than two children - thinktank

According to the report, published by the Optimum Population Trust, Britain's high birth rate is a major factor in the current level of climate change, which can only be combatted if families voluntarily limit the number of children they have.

The report calls for a 'two-child' policy in the UK that would reduce the nation's population from 60 million, as it currently stands, to no more than 55 milllion by 2050.

With the UK having the highest rate of teenage pregnancies in western Europe the thinktank is also calling for the Government to increase investment in family planning clinics and to look at ways of discouraging teenage girls from becoming pregnant.

At its current rate the report estimates that the UK's mid-century population is projected to be 68-69 million with the planet having the largest generation of young people in history - what it terms a 'youthquake'.

High population and accelerating consumption means that humans are outstripping the planet's biological capcity, says the report. By 2050, with the global population rising to 9.2 billion, humans will be using twice the Earth's natural capacity.

Figures released in the report highlight the links between human population and climate.

It claims that every additional Briton will 'burn' during their lifetime roughly the same amount of carbon as is found in a hectare of old-growth oak woodland - an area about three quarters the size of a Premiership football pitch or 50 average-sized UK gardens. Commenting on the figures, Prof John Guillebaud, the report's author, said: "Climate change is now widely regarded as the biggest problem facing the planet but most of the solutions seem to involve national or international agreements that look as far away as ever.

"We're nearing the point of no return and people are feeling increasingly desperate and helpless.

"The answer lies in our own hands. We're simply failing to acknowledge the link between human numbers and global warming.

"We have to recognise that the biggest cause of climate change is climate changers – in other words, human beings, in the UK as well as abroad - so deciding to stop at two, or at least to have one child less, is probably the simplest, quickest and most significant thing any of us could do to leave a sustainable and habitable planet for our children and grandchildren."