More than 100m Covid vaccine doses are due to expire and be “thrown away” unless global leaders urgently share surplus supplies with the world’s poorest countries, Gordon Brown has warned.

The “staggering” number of stockpiled “use now” jabs will be of no use to anyone by December, according to a new report from the research group Airfinity.

The former prime minister said the failure of Boris Johnson, Joe Biden and EU leaders to agree on a plan to distribute the spare doses meant the world was facing a “vaccine waste disaster”.

Brown has sent Airfinity’s research to leading politicians, including the US president, the UK prime minister, and senior figures in Brussels, before a global vaccine summit on Wednesday.

Airfinity said its research predicted that by the end of this month, 7bn vaccine doses would be available around the world, rising to 12bn by December.

Brown said the crucial issue was how and where the vaccines would be distributed, warning that there was no agreement on who would provide the vaccines to poor countries by December. Unless a plan was drawn up urgently, he said, lives would be lost needlessly.

“We need a vaccine release plan to provide ‘use now’ vaccines to prevent a vaccine waste disaster because ‘use by’ dates are missed,” he said.

“It is unthinkable and unconscionable that 100 million vaccines will have to be thrown away from the stockpiles of the rich countries while the populations of the world’s poorest countries will pay for our vaccine waste in lives lost.

“It will be a profound and collective political tragedy if this summit misses the opportunity to act, with doses transferred immediately to poorer countries.”

The campaign group Global Justice Now said wasting millions of doses of Covid vaccines would be an “atrocity” when they could be used in poorer countries

Its director, Nick Dearden, said: “Rich countries like the UK are hoarding vaccines that are desperately needed in low and middle-income countries.

“Poorer countries shouldn’t have to wait until our doses are about to expire to vaccinate their populations. Many are capable of safely manufacturing vaccines, if only we would waive intellectual property, so vaccines can be produced patent-free in the countries that need them most.”

Last month, the director general of the World Health Organisation (WHO), Dr Tedros Adhanom Ghebreyesus, called for a global pause of Covid vaccine booster programmes until at least the end of the year to allow all countries to get more of their populations vaccinated.

Tedros said there should not be widespread use of third doses for healthy people who were already double-jabbed.

Covax, a programme backed by the WHO to help distribute jabs to developing countries, has cut its forecast of deliveries of doses by a quarter for this year.

Speaking before Wednesday’s summit, Brown added: “The Airfinity report is a guide for world leaders to fix a more ambitious action plan. It shows we have enough vaccines either on shelves or in production even to vaccinate 70% of the global population by May next year.

“Global political leaders must match the extraordinary commitment and cooperation of scientists and manufacturers who have created the opportunity to vaccinate the entire world.”