Boris Johnson has joked veganism is a “crime against cheese lovers”.
In an interview on BBC Breakfast on Tuesday morning, the prime minister said he was not taking part in Veganuary because it requires “so much concentration”.
“I take my hat off to vegans who can handle it,” he said.
Johnson said it was “absolutely true” he was trying to lose weight but had not given up meat, eggs and dairy products.
“You can’t eat cheese, can you, if you’re a vegan? It’s just a crime against… it’s a crime against cheese lovers.”
Johnson was reported to have tried a vegan diet to get into shape during the Tory leadership campaign but had now given it up.
In 2008, Johnson rejected the idea of changing his diet as asked for by environmental campaigners.
“If they seriously believe that I am going to give up eating meat – in the hope of reducing the temperature of the planet – then they must be totally barmy,” he said.
Jeremy Corbyn, the 70-year-old outgoing Labour Party leader, has been a vegetarian since the age of 20.