Addressing MPs in the Commons via a virtual video streaming, the Prime Minister vowed to "end the era of cutting defence budgets". "It must end and it ends now," Boris Johnson told MPs. He added the budget will see a share of at least 2.2 percent of GDP, "more than any other EU country" and more than any other ally aside the United States.
The Prime Minister warned the increase in defence spending was necessary as he claimed the "international situation is more perilous than at any other time since the Cold War".
The Prime Minister vowed to restore Britain to its position as the foremost naval power in Europe.
He added that the decision to increase defence spending now will affect national security in 20 years time.
"Our national security in 20 years' time will depend on decisions we take today ... the international situation is now more perilous and intensively competitive than at any time since the Cold War."
He added: "For decades, British Governments have trimmed and cheese-pared our defence budget and if we go on like this, we risk waking up to discover that our armed forces, the pride of Britain, have fallen below the minimum threshold of viability.
"And once lost, they can never be regained. That outcome would not only be craven, it would jeopardise the security of the British people, amounting to a dereliction of duty for any prime minister.
"So I refuse to vindicate any pessimistic forecasters there may have been by picking up the scalpel yet again. Based on our assessment of the international situation and our foreign policy goals, I have decided that the era of cutting our defence budget must end, and it ends now.
"I am increasing defence spending by £24.1billion pounds over the next four years.
"That's £16.5billion more than our manifesto commitment, raising it as a share of GDP to at least 2.2 percent."
Mr Johnson said the UK could "hope for the best" and ignore the threat of terrorism and hostile states, but warned: "We might get away with it for a while before calamity strikes, as it surely would, or we can accept that our lifelines must be protected but we're content in our island and leave the task to our friends.
"My starting point is that either of those options would be an abdication of the first duty of government to defend our people.
"My choice, and I hope it will carry every member of the House, is Britain must be true to our history, to stand alongside our allies, sharing the burden and bringing our expertise to bear on the world's toughest problems. To achieve this we need to upgrade our capabilities across the board."
The Prime Minister said increased defence spending would help protect "hundreds of thousands" of jobs and create 40,000 new ones.
He told the Commons: "The returns will go far beyond our armed forces.
"From aerospace to autonomous vehicles, these technologies have a vast array of civilian applications opening up new vistas of economic progress, creating 10,000 jobs every year - 40,000 in total - levelling-up across our country and reinforcing our union."
He later added: "Our plans will safeguard hundreds of thousands of jobs in the defence industry, protecting livelihoods across the UK and keeping the British people safe."