The British politician, a member of the Conservatives, is in the Japanese capital for a three-day visit to meet with Prime Minister Shinzo Abe, as well as Olympics Minister Tamayo Marukawa.

Johnson, who was the Mayor of London when the British capital hosted the Games in 2012, told Koike to ignore criticism during the build-up to the event.

"First of all there's a euphoria when you get the games, and then a bit of anxiety starts to creep in, and it sort of goes downhill and people have all sorts of stories, we had all sorts of problems," Johnson told Koike, according to ABS-CBN News in the Philippines.

"Then when finally the games begin, after it seemed as if you could do nothing right, then you can do nothing wrong and everybody gets behind you.

"I am sure Tokyo 2020 will be a fantastic success."

Criticism has been aimed at Tokyo 2020’s budgeting but their efforts to decrease costs were praised by the International Olympic Committee (IOC) last month.

Organisers unveiled a budget of between ¥1.6 trillion (£11 billion/$13.6 billion/€13.1 billion) and ¥1.8 trillion (£12.4 billion/$15.3 billion/€14.7 billion) in January.

This included a "contingency budget" of up to ¥309 billion (£2.2 billion/$2.8 billion/€2.5 billion), with a projection by the Tokyo 2020 and the Tokyo Metropolitan Government putting the expected cost at ¥1.40 trillion (£10 billion/$12.9 billion/€11.4 billion).

Organisers have got the budget down to around $13 million (£11 billion/€13.1 billion), but IOC vice-president John Coates urged organisers and different levels of Government to continuing working towards making savings.

Tokyo 2020 were also thrust into the spotlight yesterday as it emerged that the family of a 23-year-old construction worker at the Olympic stadium who committed suicide earlier this year did so due to “overwork”,

The unnamed worker allegedly clocked 200 hours of overtime at the stadium, the planned centrepiece for the 2020 Games, in the month before his body was found in April.

He went missing in March before being found with a note saying he had “reached the physical and mental limit”.

His family have now applied for compensation and requested that his death be formally recognised as a case of “karoshi”, or death from overwork.

“Karoshi” is blamed for hundreds of deaths each year from strokes, heart attacks or suicide in a country notorious for long working hours.

Tokyo 2020 told AFP that they are “saddened” by the news.

They promised to ask operators to “take the utmost care to ensure there is no reoccurrence of such tragic events”.