Gordon Brown on Friday called on the Government to urgently speed up plans to fund covid vaccination programmes in developing countries.
The former prime minister and chancellor said wealthier countries are being “too slow” in sending unused jabs overseas.
He has organised a letter signed by 160 global leaders calling on richer countries to share their surplus doses.
It argues unless action is taken at the G20 summit, hundreds of thousands of lives could be lost.
Mr Brown said G20 leaders need to decide unused vaccines should be “moved out as quickly as possible to save lives”.
He added on BBC radio: “We’re being too slow and we’re holding back when we know we’ve got these unused vaccines... There’s also an urgency about preventing vaccines passing their use-by date.”
More than 50 countries, mostly in Africa, missed the WHO target for vaccinating 10 per cent of their populations by the end of September.
The UK, US, EU, Canada and Japan will have 1.2 billion surplus jabs by the end of the year.
The UK has pledged to donate 100 million surplus vaccines.
