Ahead of key talks on Ukraine with US President Donald Trump in Washington on Thursday, Starmer told parliament the increase would be funded by cutting overseas development aid from 0.5 percent to 0.3 percent of the economy.

Trump has demanded that NATO allies more than double their defence spending targets to five percent of economic output.

The UK spent 2.3 percent of gross domestic product (GDP) on defence in 2023/24.

Starmer's Labour government had previously committed to increasing defence spending to 2.5 percent, but had not set a timeline.

He told lawmakers there would be some "hard choices" but it would be the "biggest sustained increase in defence spending since the end of the Cold War".

The government would also "set a clear ambition for defence spending to rise to 3 percent of GDP in the next parliament," he said.

Trump has repeatedly called on European nations to boost their defence spending.

"The nature of warfare has changed significantly. That is clear from the battlefield in Ukraine, and so we must modernise and reform our capabilities as we invest," Starmer said.

"This investment means that the UK will strengthen its position as a leader in NATO and in the collective defence of our continent, and we should welcome that role".