According to a new report on food purchasing that underlines a revolution in the United Kingdom’s eating habits, one in eight Britons is now vegetarian or vegan.

A further 21 per Cent claim to be flexitarian, where a largely vegetable-based diet is supplemented occasionally with meat, which means a third of UK consumers have deliberately reduced the amount of meat they eat or removed it from their diet entirely.

The Guardian newspaper reports the findings in the annual food and drink Report from the supermarket chain Waitrose come as food choices assume an increasingly important role in the debate over countering climate change.

A series of influential reports have said that avoiding meat and dairy products is the single biggest way consumers can reduce their environmental impact on the planet, because farming animals is such a carbon dioxide (CO₂₎-intensive process.

“It’s extremely encouraging to learn how many Britons are choosing to reduce their consumption of animal products” said Nick Palmer, the head of Compassion in World Farming UK.

“Science proves that the healthiest diet is one that is plant-heavy.

“By eating less meat, fish, eggs and dairy and choosing higher welfare when we do, we can all help animals, people and the planet.”

The Waitrose report is based on research among shoppers across all British supermarket chains.

The retailer’s executive chef, Jonathan Moore, said: “Vegetarianism has grown and evolved. More people dip in and out of it.

“There was a time when choosing a plant-based diet was about taking an ethical stand based on unwavering principles.

“For many, this distinction between vegetarians and meat-eaters still exists but for others the lines have blurred.”

The number of vegans in the UK, who shun all animal products including dairy and eggs, has grown fourfold in the past four years from 150,000 to 600,000, according to the Vegan Society.

Waitrose was the first UK supermarket to install dedicated vegan sections in 134 of its stores in May.

It has also launched a range of more than 40 vegan and vegetarian ready meals.

Vegan dining out is also booming, the report notes, with the Good Food Guide highlighting restaurants with dedicated vegan menus for the first time this year after many high street chains and pubs increased their non-meat-and-dairy options.

About 60 per cent of vegans and 40 per cent of vegetarians surveyed said they had adopted the lifestyle over the past five years, with 55 per cent citing animal welfare concerns, 45 per cent health reasons and 38 per cent environmental issues.

People in the 18-to-34 age group were more likely to switch to veganism, with much less enthusiasm among the over-55s.

Waitrose’s report is based on millions of the supermarket’s transactions in shops and online, bolstered by a poll of 2000 adults who shop across a range of retailers.

Scientific research published this year found that without meat and dairy consumption, global farmland use could be reduced by more than 75 per cent, an area equivalent to the United States, China, the European Union and Australia combined, and still feed the world.