The Prime Minister on Tuesday ended 30 years of gradual disarmament by increasing the limit, from 180 to 260 warheads.
The move forms part of the new integrated review of defence and foreign policy, which will see a £24 billion investment in response to perceived threats from Russia and China.
Speaking in the Commons, the Prime Minister said: “The overriding purpose of this review, the most comprehensive since the Cold War, is to make the United Kingdom stronger, safer and more prosperous whilst standing up for our values.
“Our international policy is a vital instrument for fulfilling this government’s vision of uniting and levelling up across our country, reinforcing the Union and securing Britain’s place as a science superpower and a hub of innovation and research.
“The first outcome of the integrated review was the government’s decision to invest an extra £24bn in defence, allowing the wholesale modernisation of our armed forces and taking forward the renewal of our nuclear deterrent.
"The new money will be focused on mastering the emerging technologies that are transforming warfare, reflecting the premium based on speed and deployment and technical skill.
“All our international goals rest upon keeping our people safe at home and deterring those who would do us harm, so we will create a counter-terrorism operations centre bringing together our ability to thwart the designs of terrorists while also dealing with the actions of hostile states.”
Research last year showed just one nuclear warhead dropped on Manchester would be enough to kill 82,000 people.
The review will also see a host of cuts across the military, thought this was not mentioned by Mr Johnson during his speech.
SNP spokesperson for defence Stewart McDonald claimed the increase showed the Prime Minister was making Britain an “untrustworthy and unreliable international partner”.
He said: “Even after Covid-19, both the Tories and Labour remain wedded to an outdated, Cold War understanding of security that worships these weapons of mass destruction.
"Nonetheless it is shocking that – after slashing the aid budget and freezing pay for armed forces personnel – the Prime Minister has managed to find the cash for yet more nuclear warheads.
“For the Prime Minister to stand up and champion the international rules based system before announcing in the same breath that the UK plans to violate its commitments to the International Treaty on Non-Proliferation beggars belief.”
Labour leader Sir Keir Starmer warned there was “a very real risk” the armed forces would be “stripped back even further”.
He said: “Britain should and could be a moral force for good in the world.
"After a decade of neglect, this review was the chance to turn a corner, but there is now a very real risk that our armed forces will be stripped back even further and that this review won’t end the era of retreat. In fact, it will extend it.”