The former prime minister said it was time for the WHO to create “uniformity” in the rules by which passengers prove their Covid status to end the chaos over international travel.
“The global confusion on travel requires a global solution,” said Mr Blair. “The world cannot begin to recover from Covid without people being able to move around again. This can only be done through a common global solution.”
It comes as Mr Johnson’s government is expected to drop the 10-day quarantine requirement from countries on its amber list, while Germany has now lifted a travel ban on arrivals from the UK.
But Mr Blair said there was still a confusing lack of agreement between countries on which vaccines are accepted as valid, different testing standards and different Covid “passports” showing someone’s status.
The Tony Blair Institute has called on the WHO to take on an expanded role in bringing uniformity to vaccines, testing and Covid passports.
The think tank said national governments, particularly G20 nations, should empower the WHO to take the lead on a new travel framework.
In a new paper, the institute suggested that the WHO could prepare a report in time for the G20 summit this autumn in the hope of getting an agreement on a “global standard” for other countries to follow.
Mr Johnson and the other G20 heads of state and government will gather in Rome on 30 October.
The NHS Covid pass – showing vaccination status – is not accepted by the EU as a whole, but some countries are accepting it. The UK government hopes it will be able to forge an agreement with Brussels so it can be accepted for entry into the bloc.
Mr Blair has also urged the UK government to make “Covid passports” a mandatory requirement for entry into England’s nightclubs, music festivals, sports matches and other big events this summer.
The government has gone cold on the use of domestic Covid status certification – but the former PM said it could cut the number of infections in England by a third.
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