The UK’s national security is under severe threat from the climate crisis and the looming collapse of vital natural ecosystems, with food shortages and economic disaster potentially just years away, a powerful report by the UK’s intelligence chiefs is due to warn.

However, the report, which was supposed to launch on Thursday at a landmark event in London, has been delayed, and concerns have been expressed to the Guardian that it may have been blocked by number 10.

The destabilising impact of the climate and nature crises on national security is one of the biggest risks facing Britain, the joint intelligence committee report is understood to say.

Already, food import supply chains are coming under pressure, with the price of some commodities increasing. This could be exacerbated in the near future, the defence experts have warned, with the UK over-dependent on imports.

Other industries will also be affected by ecosystem collapse in places such as the Amazon and by the worsening impacts of extreme weather around the world. These impacts will not be encountered far off in the future as some had complacently assumed, ministers have been told, but are already being felt and will grow in significance as temperatures rise beyond 1.5C above preindustrial levels.

The hard-hitting report was to be published on Thursday at a landmark event in London. But the Guardian understands that the report, prepared by experts over many months, has been halted.

One source told the Guardian they feared it was being suppressed because the government was unwilling to face the issues raised. Overseas aid, formally known as official development assistance (ODA), which could help to stabilise countries most at risk from the climate crisis and avoid some of the impacts warned about, has been slashed.

“This is a very stark warning,” another source familiar with the contents told the Guardian. “It is very clear that the impacts on national security are very worrying.”

Food is the biggest risk as the UK imports an increasing proportion of its food from overseas, some of it coming from areas known to be at risk of climate disaster and ecosystem collapse. The clothing and fashion industry is also already feeling the strain as many fabrics come from areas at risk.

Migration from countries worst affected by the climate and biodiversity crises will also have an impact on society and the economy. Some of the countries worst affected are likely to see governments fall and the rise of social disorder, leading to political instability that in turn will have an impact on the UK’s security.

Defence chiefs have been warning about the climate crisis for two decades, and the UK was the first country to force a discussion of the issue at the UN security council in 2007. But little has been done since to address the impacts of climate breakdown and ecosystem collapse on national security.

Defence experts have grown increasingly concerned at the lack of action, and some have called for climate finance to be considered part of national security spending.

The UN’s Cop30 climate summit, to be held next month in Brazil, is likely to show that most nations are well behind on targets to cut greenhouse gas emissions drastically, in order to prevent global temperatures exceeding 1.5C above preindustrial levels. Prime minister Keir Starmer was expected to go to Cop30, where the UK can boast about some of the world’s most ambitious targets and solid achievements in cutting emissions. But the Guardian understands that some of his advisers want him to stay at home, fearing that the Reform Party will attack him for going.

The government has been approached for comment.

Zac Goldsmith, a former Conservative minister under Boris Johnson, said tackling the nature crisis must have equal priority to the climate crisis as a defence issue.

“There are plenty of nature backers in Labour, but with David Lammy moved from the Foreign Office, it’s very clear that nature has been drastically deprioritised and we are left with a one-dimensional focus purely on carbon,” he said. “Starmer looks to be the first British PM to not attend a Cop so as to avoid being exposed for turning up empty-handed and even dropping existing commitments.”

Goldsmith added: “There’s no sign currently that the UK will back [Brazilian] President Lula’s groundbreaking plan to reverse destruction of the world’s great tropical forest basins, even though it was constructed with much UK input. Some of our best-loved and most respected programmes are at risk of being killed off [from ODA cuts]. And despite leading in every way on global ocean protection, we are now being blamed for hampering progress towards protecting the Antarctic.

“Now it seems a seminal report by the joint intelligence committee on the threats to UK security of the collapse of critically important ecosystems is being swept under the carpet by a government embarrassed by its failure to provide any leadership on the issue.”