Boris Johnson has suggested journalists should be careful while criticising without putting themselves in the Prime Minister’s shoes.

Having been the editor of the influential conservative magazine The Spectator, and covered the European Union as the Telegraph’s Brussels correspondent, Mr Johnson told a classroom of a moment in his life when a “light bulb went off in my mind”.

“I was like a journalist for a long time. I still am really, I still write stuff,” he said during a discussion at Sedgehill Academy in Lewisham, south London, on Tuesday.

“But when you’re a journalist, it’s a great, great job, it’s a great profession, but the trouble is that you sometimes find yourself always abusing people or attacking people.

“Not that you want to abuse them or attack them, but being critical when maybe you feel sometimes a bit guilty about that because you haven’t put yourself in the place of the person you’re criticising.

“So I thought I’d give it a go.”

The Prime Minister’s press secretary Allegra Stratton insisted Mr Johnson was commenting on the media’s role in holding the Government to account.

She told reporters: “That is the Prime Minister talking about the fact that you, all of you – and indeed James Slack (the No 10 director of communications) and myself once upon a time – as journalists your job is to constantly challenge and that’s something that makes all of us in Government better.”