The Prime Minister made the declaration on Wednesday, less than 24 hours after claiming “greed” and “capitalism” were behind the UK’s vaccine success in a joke about the procurement with Tory colleagues at the 1922 Committee.
Speaking on a Zoom call, Mr Johnson had said: "The reason we have the vaccine success is because of capitalism, because of greed my friends.
"Actually I regret saying it. Forget I said that."
Mr Johnson’s remark had risked escalating a row with the European Commission over access to vaccines, with the organisation’s president Ursula von der Leyen threatening a ban on exports of jabs to the UK with AstraZeneca yet to supply the doses expected to the bloc.
EC vice-president Valdis Dombrovskis told a Brussels press conference on Wednesday that AstraZeneca has “only delivered a small portion of its agreed contractual commitments” with the EU.
The European Union has exported at least 43 million doses of the various vaccines to 33 countries since the end of January, he said, but new conditions of reciprocity and proportionality would be imposed.
Mr Johnson told the Commons liaison committee on Wednesday: “The partnership we have with our European colleagues is very, very important, we continue to work with them.
“Vaccines, as you know, are the product of international co-operation. I don’t think that blockades of either vaccines or of ingredients for vaccines are sensible, and I think that the long-term damage done by blockades can be very considerable.
“I would just gently point out to anybody considering a blockade or an interruption of supply chains that companies may look at such actions and draw conclusions about whether or not it is sensible to make future investments in countries where arbitrary blockades are imposed.”
The UK Government and the European Commission sought to dampen the row on Wednesday evening by issuing a joint statement on co-operation in fighting the Covid-19 pandemic.
The statement said: “We are all facing the same pandemic and the third wave makes cooperation between the EU and UK even more important.
“We have been discussing what more we can do to ensure a reciprocally beneficial relationship between the UK and EU on Covid-19.
“Given our interdependencies, we are working on specific steps we can take – in the short, medium and long term – to create a win-win situation and expand vaccine supply for all our citizens.
“In the end, openness and global co-operation of all countries will be key to finally overcome this pandemic and ensure better preparation for meeting future challenges.
“We will continue our discussions.”
Mr Johnson’s comments linking “greed” to the UK vaccine success had earlier sparked a furious backlash, with campaigners pointing out it was actually due to universities.
Nick Dearden, director of the group Global Justice Now, said: “The Prime Minister will call this comment a slip of the tongue, but it’s an incredibly revealing remark.
“It shows just how warped his understanding of this crisis is.
“We have a vaccine because of massive public investment and the remarkable work of scientists at publicly-funded universities.
“We’ve rolled it out because of our incredible National Health Service.”
Lib Dem frontbencher Layla Moran said Mr Johnson's claim was "not helpful", while Labour MP Angela Eagle added: “Altruism, not greed, will get us through this."
Labour MP Barry Sheerman said the comments were “no surprise” as “everyone who knows our Prime Minister well understands his admiration of selfishness and greed'”.
Lib Dem MP Alistair Carmichael said: "Yet again the mask slips and what we see of Boris Johnson is ugly right-wing conservatism.
"The real story of our vaccine success is the work of our medical staff and volunteers - selflessness, not selfishness.
"It speaks volumes that Boris Johnson sees profit first and people second in the middle of a pandemic."
Plaid Cymru's Westminster leader Liz Saville Roberts added: "It's in the throw-away comments that the PM reveals himself. Greed will destroy us."
It follows Mr Johnson’s remarks on the anniversary of the UK's first lockdown on Tuesday, where the Prime Minister praised the public for showing "endurance" over the past year.
A Downing Street spokesman declined to comment on what had happened during the meeting, but refused to deny the remarks were made.
One MP insisted it was a “complete joke”, and the PM was talking about AstraZeneca "being philanthropic in non-profit production".
They added: "It's pretty cheap to distort the meaning for political gain.”
Home secretary Priti Patel on Wednesday morning defended the role played by pharmaceutical companies and Mr Johnson’s comments.
She told Sky News: “The Prime Minister always acknowledges the strong success we’ve had in terms of the vaccine, not just the rollout, which is incredible, but also our ability as a country to develop the vaccine, the role that pharmaceutical companies and science and technology has played in that.
“And actually I think that speaks to a great strength we have as a country.
“And linked to that, of course, look at our contributions to Covax, the international scheme, to get the vaccine supplies elsewhere and demonstrate that we are a very, very strong force for good internationally when it comes to vaccines, science and pharmaceutical development.”
Wales Office minister David Davies insisted the comment had been “totally out of context” and was a reference to the movie Wall Street, in which Michael Douglas’ character Gordon Gekko says “greed, for lack of a better word, is good”.
The Conservative MP said: “He made it absolutely clear that was a joke. It was a reference to the film Wall Street.
“Somebody has taken this totally out of context for their own reasons. It was a private meeting.
“I think whoever was leaking that was being pretty irresponsible and needs to go take a hard look in the mirror, frankly.”