The West faces a “deadly quartet” of Russia, China, Iran and North Korea, the head of the Government’s root-and-branch defence review has warned.

Former Nato chief Lord Robertson of Port Ellen said the four states were “increasingly working together”.

Vladimir Putin has relied on supplies from the states to wage his war in Ukraine, with Iranian drones, North Korean munitions and Chinese components sustaining his ability to attack despite Western sanctions.

The strategic defence review launched by Sir Keir Starmer’s administration will examine how to strengthen UK homeland security, bolster Ukraine in its fight against Russia, and modernise and maintain the nuclear deterrent.

It will also set out a roadmap on how to reach Sir Keir’s target of spending 2.5% of gross domestic product – a measure of the size of the economy – on defence.

Former prime minister Rishi Sunak had set a 2030 goal for spending 2.5%, at a cumulative cost of £75 billion over six years, but the new Labour administration has yet to commit to a timetable.

The co-operation between Mr Putin and his allies has alarmed Western leaders, with Nato’s summit in Washington last week declaring that Beijing and Moscow had a “deepening strategic partnership” while Iran and North Korea are “fuelling Russia’s war of aggression”.

The Washington summit declaration said China had become a “decisive enabler” of the Russian war effort through the supply of components to the defence industry.

Lord Robertson told reporters: “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 Labour peer, a former Nato secretary general and defence secretary, will work with former US presidential advisor Fiona Hill and ex-joint forces command chief General Sir Richard Barrons.

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.”

As part of the process, a defence review team will be established to engage with serving and retired members of the armed forces, the defence industry, the general public, academics, Parliament and the UK’s allies.

Defence Secretary John Healey will oversee the review and he will be regularly updated on progress, in addition to the Prime Minister and the Chancellor.

Mr Healey 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.

“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.”

Labour’s manifesto had committed to conduct the review within its first year in office, but Sir Keir wants the work to be completed much sooner.