Ministers are facing growing criticism for putting France on the new “amber plus” travel list, after concerns were raised about whether they focused too much on variant cases in its Réunion Island territory 5,700 miles (9,180 km) from Paris. The UK foreign secretary, Dominic Raab, admitted on Thursday the decision to impose tougher restrictions on millions of fully vaccinated French citizens and Britons holidaying or living across the Channel was partly due to the prevalence of the Beta variant on Réunion. He defended the move, saying it was “not the distance that matters” but rather “the ease of travel between different component parts of any individual country”. France was put on England’s amber plus list two weeks ago, after the government took advice from the Joint Biosecurity Centre (JBC). At the time, the reason given by the Department of Health and Social Care was the “persistent presence of cases in France of the Beta variant”, but a diplomatic row with France began gathering pace. In a stern rebuke of the JBC, Mary Gregory, a deputy director at the Office for Statistics Regulation, wrote to the organisation, criticising it for “not making the data and sources clear” for its advice on France. She said there was confusion about “whether cases from overseas territories had been excluded for France” and that refusals to publish clear evidence underpinning the decision “fall short of our expectations on transparency”. Gregory said the JBC had confirmed one of the ways it tracked variants was the Global Initiative on Sharing Avian Influenza Data (Gisaid), which showed there had been 1,023 Beta cases in Réunion – equal to about a third of the total number discovered across mainland France, 2,974. Réunion is still on England’s normal amber list even though the ratio of Beta cases to people is much higher, granting anyone travelling from the island who is fully vaccinated exemption from isolation on arrival, so long as they get two negative tests. The Gisaid figures revealed the number of Beta cases across France had grown by just 1.9% in the past four weeks – significantly less than Spain, where they have risen 14.2% across the same period. Sir David Spiegelhalter, who sits on the government’s Scientific Advisory Group for Emergencies (Sage), said it was clear Raab had acknowledged the decision on France was mainly based on data from Réunion and that this should have been made clear at the time. Spiegelhalter said the reasoning for putting France on the amber plus list “was unclear, to say the least”, adding that “the data behind such important policy decisions should be transparently available”. Data gleaned from random samples of positive tests showed Beta prevalence fell from about 7% in late April to 2.8% by the end of June in mainland France, according to that published by French authorities on 19 July. Only days earlier did UK ministers decide that travellers returning to England from France would be forced to quarantine even if fully vaccinated. Sylvia Richardson, the director of the MRC biostatistics unit at the University of Cambridge and president of the Royal Statistical Society, said she started looking into the data when the UK decision on quarantine policy was announced. “I had some suspicion that there was some confusion,” she said, adding that the UK government should have conferred with the French authorities before making its decision. Before 19 July, French authorities were publishing information on variant prevalence for mainland France and its territories as one number – but the geographical differences compelled them to publish the numbers on mainland France separately. Jim McMahon, the shadow transport secretary, said the traffic-light system was so “baffling” that ministers were “confusing themselves”. “We cannot continue to rely on the government’s interpretation of the figures, particularly when they are seemingly only capable of updating the public and the travel industry either via the press or social media,” he said. Layla Moran, a Liberal Democrat MP and chair of the all-party parliamentary group on coronavirus, said there was incoherent messaging about the reasons for the decision and urged ministers to lay out “clear justifications for any changes made with regards to international travel”. She added: “This slapdash approach will only continue to undermine public confidence in government decisions, at a time when clarity and caution are crucial.” France on Wednesday hit out at England’s decision to make it the only EU country excluded from new rules allowing fully vaccinated travellers jabbed on the continent or in the US to avoid quarantine, if coming from an amber list country. The Europe minister, Clément Beaune, said it was “excessive”, telling France’s LCI TV: “It’s frankly incomprehensible on health grounds. It’s not based on science and discriminatory towards the French. I hope it will be reviewed as soon as possible; it’s just common sense.”