The Prime Minister visited Yeadon, outside Leeds, this morning and started his day by helping load milk and orange juice bottles onto a delivery vehicle.
Yeadon is in the Pudsey constituency, where Tory Stuart Andrew had just a 331 majority at the 2017 election.
Asked about the narrowing polls, Mr Johnson told broadcasters: "This could not be more critical, it could not be tighter - I just say to everybody the risk is very real that we could tomorrow be going into another hung parliament.
"That's more drift, more dither, more delay, more paralysis for this country."
Pressed on whether he was nervous, Mr Johnson replied: "We're fighting for every vote."
Speaking to The Yorkshire Post Mr Johnson was asked whether he believed Jack’s mother Sarah and her account of what happened on their visit to the LGI earlier this month.
A photograph of Jack, who was waiting for treatment for suspected pneumonia at Leeds General Infirmary, was first published in the Yorkshire Evening Post on Sunday and Mr Johnson came in for heavy criticism on Monday when he initially refused to look at the photo on an ITV reporter's phone before taking the phone and putting it in his pocket.
Since, duplicated messages have appeared from various accounts on Facebook and Twitter, attempting to debunk the photo. The post has since been found to be fake.
Mr Johnson said: “Of course, of course, of course [I believe Jack’s mother] but let's be clear, what we're doing is we're investing hugely in the NHS and actually [at] Leeds Infirmary we are rebuilding that.
“We can only do that, because we have a dynamic one nation government that is putting the biggest ever cash boost into the NHS.
He added: “The worst thing for this country would be to stay paralysed, to stay frozen in the way that we are wrangling, arguing about Brexit, we need to get Brexit done, move forward.
“We've got a deal, ready to go. We can come out of the EU. On January 31, we can honour the wishes of the people. Finally, after three and a half years, and I really suggest - I really hope - that people will vote for the one nation Conservative majority.”
Mr Johnson was also asked about Dr Jason Aldiss, the former Conservative Association Chairman in Pudsey, who resigned when Mr Johnson was made leader and has been vocal in speaking out against him.
He said: “Well, I have to say that we have a united Conservative Party, every single candidate this election - it is quite incredible, never seen anything like it in history - because everybody, every single candidate is supporting the deal that I've done on the EU and that's a lovely thing, think about the spectrum of views in the Tory party on the EU.”
The PM was also pushed on what investment he would give to Yorkshire to protect against future flooding, after early on in the campaign Mr Johnson was criticised for his response to the disaster in South Yorkshire.
Asked whether he would commit to giving the £25m needed to complete, in full, flood defences in Leeds he said: “We're putting £4bn into flood defences, it's in the manifesto we've already put in £2.6bn, and we'll do everything we can to protect the people of Leeds and everywhere in Yorkshire.”
He added: “I just want to say to everybody in Yorkshire that this is a crucial moment for our country, crucial moment for the nation.”
Mr Johnson later delivered a crate of milk and other items to a house in Guiseley.
Two bottles of milk already outside the property were removed before the PM arrived.
He knocked on the door, which was opened by civil servant Debbie Monaghan, 40, who said: "Look who's here."
She called to her husband Mark, 40, and said: "So nice to meet you, Prime Minister. What are you doing up so early?"
Mr Johnson said he was delivering milk, orange juice, washing up liquid and other things before reiterating campaign pledges.
Mr Monaghan, who works for Northern Powergrid, said: "It's a surprise. It's very early, I assume he's travelled a long way but I'm going to vote Conservative so I'm quite pleased."