The former NATO chief Lord Robertson of Port Ellen who is the head of the new major defence review has warned the UK of the “deadly quartet.”

He warned that Iran, Russia, China and North Korea are “increasingly working together” as we are now living in a more “dangerous and volatile world.”

Lord Robertson said: “We’re confronted by a deadly quartet of nations increasingly working together, and we in this country, and the NATO alliance that met so successfully last week, has got to be able to confront that particular quartet as well as the other problems that are pervading the world at the present moment.”

The Prime Minister has launched a review of the UK’s defence as Sir Keir Starmer has a target of 2.5% gross domestic product (GDP) of defence spending.

The Prime Minister said, “We live in a more dangerous and volatile world. My Government will forge a new clear-eyed approach to our national defences, equipping us to tackle international threats head-on while keeping the British people safe and secure.

“I promised the British people I would deliver the change needed to take our country forward, and I promised action not words. That’s why one of my first acts since taking office is to launch our strategic defence review.

“We will make sure our hollowed-out armed forces are bolstered and respected, that defence spending is responsibly increased, and that our country has the capabilities needed to ensure the UK’s resilience for the long term.”

The Defence Secretary John Healey is to oversea the review and he will update Sir Keir and the Chancellor Rachel Reeves.

The Defence Secretary said, “At the start of a new era for Britain, we need a new era for defence.

“Hollowed-out armed forces, procurement waste and neglected morale cannot continue. Meanwhile, we need to be clear-eyed about the threats we face, with the world becoming more volatile and technology changing the nature of warfare.

In response, our armed forces need to be better ready to fight, more integrated and more innovative. We need clearer accountability, faster delivery, less waste and better value for money.

“The review will ensure that defence is central to the future security of Britain and to its economic growth and prosperity.

“This new era requires a new type of review that moves at pace. The Prime Minister and I will therefore draw on both external military, industrial and foreign policy experts, and those from inside Government, to help set the path for Britain’s defence for the next decade.

“Together, we will make Britain secure at home and strong abroad.”