Investment in renewable energy should be counted under defence expenditure, says a group of retired senior military personnel, because the climate crisis represents a threat to national security.

They have called for increased spending on low-carbon power as a way of making the UK and other European countries more resilient to threats from Russia and other potential aggressors.

Nato members have pledged to spend 3.5% of GDP on their armed forces, weapons and other “core” items of defence spending, plus a further 1.5% on “critical infrastructure”, such as civil preparedness.

Low-carbon energy should be included in the 1.5% pledge, the group of military experts argued in a letter to European heads of government seen by the Guardian.

“We must end our dependence on foreign oil and gas,” they wrote. “A reliance on fossil fuels makes our countries less secure. It leaves us susceptible to huge price spikes during times of conflict – as we saw when Russia invaded Ukraine.”

They added: “To help unlock the investments needed to achieve energy sovereignty, and ensure we stop handing over billions of dollars a year to the Kremlin, we urge you to push for spending on renewable and low-carbon energy to be counted as part of the Nato 1.5% target.”

Retired Lt Gen Richard Nugee, one of the signatories of the letter, told the Guardian that investing in renewable energy was more secure than seeking more gas supplies, as some have urged, because wind turbines, solar panels and other forms of renewable energy are more dispersed and thus less vulnerable to attack.

“To have a strong military deterrence, we need a resilient homeland,” he said. “If we want to build a resilient country, low-carbon energy is a very important component.”

V Adm Ben Bekkering, a former senior Royal Netherlands Navy officer and currently partner of the International Military Council on Climate and Security, said governments must take a broader view of threats. “We need to find ways to look at security from a wider perspective than just the military,” he said. “By finding ways to increase our military, economic and ecological sustainability, we stand a chance [against aggression].”

The other signatories include: Tom Middendorp, former chief of defence of the Netherlands; Air Marshal Sir Graham Stacey, former chief of staff of Nato Allied Command Transformation; R Adm Neil Morisetti, former senior Royal Navy officer and now professor of climate and resource security at University College London; retired Brig John Deverell, former UK director of defence diplomacy; and retired Lt Gen Richard Wardlaw, chair of the Centre for Economic Security and former chief of defence logistics in the UK Strategic Command.

There is growing awareness among senior military figures of the potential impacts of the climate crisis, but it is not clear whether heads of government are prioritising the issue. Downing Street earlier this month suppressed publication of a major report by the Joint Intelligence Committee that warned the UK would be at risk if large ecosystems overseas, such as the Amazon, were to collapse.

Many countries are cutting back spending on overseas aid, including helping poorer countries afflicted by the climate crisis, even while expanding their defence budgets. But several senior experts have said that governments should consider putting more money into overseas climate finance, in their own interests, and that they should finance this from their national security budgets.

Gareth Redmond-King, head of the international programme at the Energy and Climate Intelligence Unit thinktank, said: “Clean energy is the route to net zero – the only solution we have to halting climate change and avoiding ever worsening impacts. And clean energy offers greater national security, if we want to end our reliance on authoritarian states that control so much of the world’s fossil fuels, at least one of whose wars have driven up household energy prices so much in recent years.”