Following the disclosure, the Mayor of London said: "I don't think anybody in this city is shocked about what consenting adults do. As long as you don't involve children, animals and vegetables, they leave you to get on and live their own life in their own way."

As well as two young children by his partner Emma Beale, he has two older daughters by one woman and a son with another, the BBC reported.

The information about the three other children, previously unknown to the general public, comes ahead of the publication of an unauthorised biography by journalist Andrew Hosken later this month.

Mr Livingstone told the BBC: "What happens in my private life is a matter solely for me and the people that share my private life.

"If I had secrets that my family or my close friends didn't know about then that would be a different matter. But there's a difference between private and secret and I think the media's got to understand that."

The book Ken: The Ups and Downs of Ken Livingstone is published by Arcadia Books.

Author Mr Hosken, a journalist on BBC Radio 4's Today programme, has previously written an unauthorised biography of Dame Shirley Porter.

Following the report, Mr Livingstone's campaign said: "Ken never discusses the private life either of himself or of his opponents. He has no intention of discussing in this election either the private life of Boris Johnson, Brian Paddick, or himself.

"What Londoners want to discuss in this election is transport, crime, housing, good community relations and the environment."