Interviewed on the ITV daytime show, the Prime Minister blamed a "broken" Parliament once again for the UK not leaving the EU on October 31.
"I think that is basically because after three-and-a-half years we haven't got done what we told the people we would do in 2016," he said.
Mr Johnson gave Phillip Schofield and Holly Willoughby a "rock solid guarantee" that no part of the NHS would be sold off, dismissing Labour's claims the health service was "on the table" in trade talks with the US as "complete nonsense".
"Instead, what we are doing, as a One Nation Conservative government, we're investing massively in the NHS," he said.
The Prime Minister defended the proposal of taxing would-be NHS workers coming from the European Union after Brexit, saying people coming to the UK "should make a contribution".
The Conservative Party leader also stuck to committing to bringing in 50,000 new nurses - despite telling listeners on LBC radio last week the figure was inflated and included 19,000 existing nurses.
When challenged by Mr Schofield, the Prime Minister insisted "we will have 50,000 new nurses."
Mr Johnson said: "First of all we're bringing in the bursary back, the £5,000 a year bursary, which I think will make it more attractive and easier.
"We're also in the short term, going to deal with the shortage by something I think is very much appreciated by the NHS, and that is squeezing the time that people have to wait to get their visa to come and be nurses in the NHS."
In response to the Prime Minister's answer, Phillip Schofield read out a comment from one of This Morning's doctors, Sara Kayat, who said a "nurse tax", which would include paying for visa fees, immigration and health surcharges - could cost families up to £10,000 in their first five years in the UK.
The Conservative leader said: "I don't quite know what Sara means but it is only fair that people who come to this country make use of our services, from wherever they come from, should make a contribution.
"I think that's reasonable."
Pressed on people's lack of trust in him, Mr Johnson said: "I think there is a big trust issue with the whole of politics at the moment," he said.
"We asked them to vote in the EU referendum, they did deliver a result and for the last two to three-and-a-half years we have been wrangling.
"I got to the stage as Prime Minister where it was obvious we couldn't get this thing through Parliament."
Mr Johnson's appearance on the long-running TV show came two days after Labour leader Jeremy Corbyn told Phillip and Holly he was for "everything that has happened" in his party regarding anti-Semitism.