Investment in renewable energy should be counted under defence expenditure, a group of retired senior military personnel have said.

The group said it is because the climate crisis represents a threat to national security and have called for increased spending on low-carbon power as a way of making the UK and other European countries more resilient to threats.

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, and reported 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.”

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.

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