Keir Starmer has warned his successor not to borrow more to pay for defence as he raided energy, transport and housing projects to plug a military spending deficit with an extra £15bn over the next four years. The prime minister revealed his long-awaited defence investment plan (Dip) on Tuesday, after an 11-month government row that cost him a defence secretary and arguably contributed to his downfall. Starmer said the government had found the £15bn for the plan by taking money from road and energy schemes.

A £9bn scheme to upgrade military housing over the next decade has been adjusted so costs fall after 2030. It was a £1.5bn improvement obtained by the new defence secretary, Dan Jarvis, who is fighting to keep his job after Starmer leaves, compared with the £13.5bn offered to John Healey, who resigned in protest at the money he had been offered. In his introduction to the investment plan, Jarvis said the extra money was needed because Labour had “inherited a defence programme that was underfunded, overcommitted, and insufficiently attuned to the threats we now face.

47 out of 49 programmes were delayed or over budget”. Overall defence spending will rise marginally from 2.6% of GDP in 2027 to 2.7%, or nearly £80bn, by 2030, which Starmer said would put the UK “on a trajectory” to hit 3% in the next parliament. As the plan emerged, Healey said the budgets were too small.

“Britain will still be spending just 2.7% of GDP in 2030, the date when Nato has warned we could face a Russian attack,” he said. A clear target date to hit 3% was necessary, he added. Starmer urged his successor, likely to be the Labour MP Andy Burnham, to find more money for defence at the next spending review, though he warned not to borrow more to pay for it.

The outgoing prime minister said defence “must be the number one priority at the next spending review”. The Nato target, agreed by Starmer, is to reach 3.5% by 2035. The Guardian revealed last week that some of the prime minister’s allies would use the transition period to recommend Burnham revive the idea of “defence bonds”, which was previously rejected by the Treasury.

“Defence bonds are just borrowing by another name,” he told an audience at a drone-making company in Berkshire. “We’ve looked at this very carefully, but the fact is doing this through borrowing will push interest rates higher at a time when £1 in every £10 already goes on paying their interest. “This government has fought hard to bring the public finances under control, and it has paid off helping to bring inflation and mortgage rates down.

We should not sacrifice that.” The prime minister’s plan means the government will now spend an extra £15bn on defence over the four years between 2026-7 and 2029-30, beyond the £283bn it had previously allocated. It comes at a time when, according to the full 80-page plan released in the afternoon, “demands on defence are rising”. It warns that Russian “aggression is growing around our shores”, that the Iran war has reinforced the need to boost air and missile defence and that “the US is rightly demanding that Europe steps up”.

Key programmes that will be funded over the four years include: £47bn on new nuclear submarines, including the Dreadnought replacement for the Trident submarines and the new Aukus attack submarine project, being developed with Australia and the US.