Save the Children, Wellcome Trust and few other group of charities have urged UK Prime Minister Boris Johnson to donate Covid-19 vaccine to the poorer countries through Covax.
UK's Culture Secretary Oliver Dowden said the UK does not currently have a surplus of vaccines, but when it does that surplus will be shared, reports the BBC.
In a letter, the charities said the UK is "one of the world's highest per-capita buyers" of vaccines and is on track to have more than 100 million surplus doses.
"There is therefore the high risk that the UK will be hoarding limited supply whilst health workers and the most vulnerable in low and middle-income countries do not have access," the letter said.
"The UK will be sitting on enough surplus vaccine doses to vaccinate the world's frontline health workers twice over."
The group urgeed the UK to immediately begin donating doses through the Covax initiative.
The UK, which has ordered 400 million vaccine doses and will have many left over, has said it will donate most of its surplus vaccine supply to poorer countries.
The lower income countries most likely to receive the first vaccines through Covax include Afghanistan, Haiti, DR Congo, Ethiopia and Somalia.
More than 29 million UK adults have received a first dose of a Covid vaccine so far.