The United Kingdom government on Thursday said that coronavirus vaccination certificates from all countries must meet a “minimum criteria” amid rising backlash over a rule requiring Indians visiting Britain to quarantine even if they are fully vaccinated, PTI reported.

After India warned of “reciprocal measures”, the United Kingdom on Wednesday included Serum Institute’s Covishield to its list of approved coronavirus vaccines. Earlier, beneficiaries who received Covishield in the United Kingdom were recognised as vaccinated, while those who got it in India were not.

Now, officials have raised doubts about the vaccine certification in India and passengers from the country will still have to undergo a 10-day home isolation.

A spokesperson of the United Kingdom government said they are working with India on a “phased approach” to ease travel guidelines.

“Our top priority remains protecting public health, and reopening travel in a safe and sustainable way, which is why vaccine certification from all countries must meet the minimum criteria taking into account public health and wider considerations,” the spokesperson added.

In an interview to NDTV on Wednesday, British High Commissioner to India, Alex Ellis, said that the United Kingdom was trying to figure out how Indian government’s CoWIN vaccination portal works. “Once we understand this better and know that it is absolutely safe, we can go ahead and remove the quarantine for Indian travellers,” he added.

Ellis also said that India was not a part of the “green-listed countries” and that there are still “some Covid-19 cases” in the country. “Most other nations on the list that do not need any quarantine are in the green category, where the number of active cases are very low in comparison,” he said.

At a Global Covid Summit hosted by United States President Joe Biden, Prime Minister Narendra Modi on Wednesday said that international travel should be made easier through mutual recognition of vaccine certificates.