Sir Keir Starmer has announced that foreign aid will be cut to boost defence spending.
The Prime Minister said spending on defence would go up from 2.3% to 2.5% of gross domestic product in 2027.
The increase will be funded by slashing overseas aid from 0.5% of gross national income to 0.3%.
Sir Keir said the move was in response to “tyrant” and as US president demands Europe spends more on security.
Speaking in the House of Commons on Tuesday, Sir Keir said: “We must find courage in our history, courage in who we are as a nation, because courage is what our own era now demands of us.
Sir Keir Starmer speaks in the Commons on Tuesday (Image: Parliament TV)
“So starting today, I can announce this Government will begin the biggest sustained increase in defence spending since the end of the Cold War.
“We will deliver our commitment to spend 2.5%. of GDP on defence, but we will bring it forward so that we reach that level in 2027, and we will maintain that for the rest of this Parliament.”
The change will mean spending £13.4billion more every year from 2027, which he said required “extremely difficult and painful choices”.
Sir Keir added that he wanted that figure to reach 3% of gross domestic product during the next parliament.
It comes ahead of the PM’s visit to Washington where he will meet Mr Trump on Thursday.
Earlier today, Tory leader Kemi Badenoch urged Sir Keir to redirect foreign aid and welfare funding towards defence spending.
In a major speech in central London, she said: “I will back the Prime Minister in taking those difficult decisions to increase defence spending.
“For example, he should consider whether some of the 0.5% currently spent on development aid should be repurposed, at least in the short term, towards defence and security.
“And he should also look at making welfare savings to fund increased defence expenditure.”