Boris Johnson has insisted he is as “fit as a butcher’s dog” for the closing days of an election which is “going to go to the wire”.

The Prime Minister dismissed any suggestions he looked “knackered”, while also playing down polls which have put the Conservatives as the frontrunners throughout the campaign ahead of Jeremy Corbyn’s Labour.

Asked if he is worried his party’s lead was slipping away as the polls tightened, Mr Johnson told reporters during a campaign visit in Wiltshire: “Of course this election is going to go to the wire. It’s very important everyone recognises the starkness of the choice.

“We can either go forward, get Brexit done, unleash the potential of this country, unleash a tidal wave of investment that we have seen is waiting to come in or else we can have Groundhog Day with two more referendums and chaos and paralysis in Parliament.”

Questioned about how he is feeling about the election and what he is doing to relax during the campaign, Mr Johnson joked: “Apart from a few quadratic equations and a little pre-Socratic philosophy.

“I’m working very hard the whole time to secure a working majority and the choice is stark for this country.”

Pressed on whether he is knackered or not, Mr Johnson replied: “Do I look knackered? I’m like a steel spring, I’m as fit as a butcher’s dog.

“I’m like a coiled something or other – spring, a coiled spring.”

But he offered no indication that he would follow Mr Corbyn and other leaders in facing Andrew Neil for a grilling on the BBC.

Mr Johnson said: “I’m going to be doing all sorts of media engagements in the course of the next few days and I defer to others in this room who will be happy to advise about that kind of thing.

General Election 2019
The Prime Minister dons a life vest for a trip to the Port of Southampton (Stefan Rousseau/PA)

“Come on, I think I’m the first Prime Minister to have done a head-to-head TV debate; I did the Question Time thing; I’ve done hours and hours of phone-ins.

“I think I’ve fielded more questions at press conferences than any other leader standing at the election. Here I am, I don’t think I have been unscrutinised.

“As Socrates said, the unscrutinised life is not the life of a man.”

He was also asked if he would guarantee Cabinet positions for his top team, including Priti Patel as Home Secretary and Dominic Raab as Foreign Secretary.

Mr Johnson said: “All such questions come firmly in the category of measuring up the curtains, and it’d be a mistake to do so.

“There are nine days to go, it is a very, very tight election and the choice is critical for the country, absolutely critical.”