Boris Johnson may have given his strongest hint yet that he intends for HS2 to go ahead after telling a 10-year-old interviewer that the way forward was to “keep digging”.

His comment came as he was quizzed as part of a children’s news programme for Sky.

Asked if he could explain more about the high-speed railway line, Johnson said so far money had been wasted and the project had been poorly managed.

In his answer to primary school pupil Braydon Brent during the meeting in Downing Street, he said: “Now the truth is, the people who did it spent far too much money, they were profligate with the way they did it. Do you know what I mean by profligate? They just wasted money.

“So we’re in a hole, we’re in a mess. But we’ve got to get out of it. And we need a way forward, so we’re thinking about how to sort it out now.”

To move on, the prime minister said: “In a hole the size of HS2, the only thing to do is keep digging.”

Braydon, whose interview is aired on FYI on Saturday, said: “Keep digging?”

Johnson said: “That’s what you’ve got to do. It’s a big hole.”

It is the closest indication he has given so far on his personal thoughts on the project, with a formal announcement expected next week.

The prime minister has only been interviewed once in 2020 by a journalist, the BBC’s Dan Walker on BBC Breakfast. He is increasingly using more direct methods of communication with the public, including his live question-and-answer sessions via Facebook called “the People’s PMQs”.

A final decision on whether the rail project linking London to Birmingham, Manchester and Leeds, will go ahead is still to be formally announced.

Sajid Javid, the chancellor, publicly swung behind the scheme despite the spiralling costs, cited as £106bn.

Conservative politician Andy Street, regional mayor for the West Midlands, said there was a strong economic case for HS2 to go ahead and it would be foolish to turn the tide on a project intended to rebalance the north of England.

Some senior figures in government, including Johnson’s chief aide Dominic Cummings, are not keen on the multibillion-pound scheme. A host of backbenchers are concerned about its damage to the countryside.