BRITAIN will spend 3% of GDP on defence with ten-year plan, set to be revealed in days, “unaffordable” without commitment.

Defence secretary John Healey revealed that the defence spend ambition was now a certainty in an interview with The Times.

The government’s ten-year defence plan is set to be unveiled on Monday.

Sources said on Wednesday that the 3% of GDP target remained an ambition.

However, Defence Secretary John Healey has now told The Times: “In the next parliament this country will spend 3 per cent of our GDP on defence.”

Healey added: “It allows us to plan for the long term. It allows us to deal with the pressures.”

It remains unclear if the commitment has been agreed across Whitehall.

The defence spending review, which was due to be published on VE Day, was reportedly delayed because of disagreements between the Treasury and the Ministry of Defence.

An increase spend to 3% of GDP would see the country cough up £10 billion more for defence each year than it currently does.

The upcoming review is said to be massive, about 130 pages long, and will not include any plans to cut armed forces numbers.

It assumes that the 3% target will be met by 2034, if it isn’t Britain’s decade long modernisation plan will not have the funding it needs.

The review was drafted with troops from America, France and Germany embedded in the team to ensure a collaborative approach with the UK’s closest allies.

A source said the plan was “really slow” to make it affordable over time.

The review is scalable and programmes can be sped up if Starmer decides to spend more on defence.

Under current spending assumptions some of the modernisation projects could take years to complete.

In February the Prime Minister announced an plans to increase defence spend to 2.5% of GDP by 2027.

The 3% “ambition” was announced as a goal to reach by 2034.

Military chiefs have warned that the UK is not prepared for the possibility of a future war with Russia.

The US administration has privately urged the UK to increase defence spending, calling the current 2.3% spend an “irritant.”

NATO members are expected to commit to an increased defence spend, possibly as high as 3.5%, during a summit in June.

A Ministry of Defence spokesman said: “This government has announced the largest sustained increase to defence spending since the end of the Cold War — 2.5 per cent by 2027 and 3 per cent in the next parliament when fiscal and economic conditions allow, including an extra £5 billion this financial year.

“The review will rightly set the vision for how that uplift will be spent, including new capabilities to put us at the leading edge of innovation in Nato, investment in our people and making defence an engine for growth across the UK — making Britain more secure at home and strong abroad.”