Imposing vaccine passports is likely to make hesitant people even more reluctant to get Covid jabs, research involving more than 16,000 people has found as Downing Street vowed to press ahead with the plan within a month.

Boris Johnson announced in July that the government would make it compulsory for nightclubs and other crowded indoor venues to ensure customers have been fully vaccinated before allowing them entry.

No details have yet been published, prompting speculation the plan would be ditched in the face of a backlash from Conservative backbenchers and business groups. But the prime minister’s official spokesperson said on Tuesday there was no change in the policy.

“We set out broadly our intention to require vaccination for nightclubs and some other settings. We will be coming forward in the coming weeks with detail for that,” he said.

As well as helping to protect clubbers from the virus, the move is aimed at boosting vaccine uptake – but the research, to be published in the Lancet journal EClinicalMedicine this month, suggests it could be counterproductive among the most hard-to-reach groups.

The survey was carried out in April when most people were either unvaccinated or had received only one dose of a vaccine. It suggested the groups that are less likely to get vaccinated – including the young, non-white ethnicities and non-English speakers – also view vaccine passports less positively.

“This creates a risk of creating a divided society wherein the majority are relatively secure but there remain pockets of lower vaccination where outbreaks can still occur,” the authors wrote in the paper, which is currently in preprint form.

The analysis involved 16,527 people, of whom 14,543 had not yet had both vaccine doses. In this group, the vast majority (87.8%) indicated their decision on being jabbed would not be affected by the introduction of passports.

However, of the remaining 12.2%, about two-thirds suggested they would be less likely to get vaccinated if passports were introduced, while the rest said they would be more inclined. Vaccine passports were viewed less negatively by this group if they were only required for international travel rather than domestic use.

The lead author Dr Alex de Figueiredo from the London School of Hygiene and Tropical Medicine, said these percentages become significant when scaled up to the whole population.

Younger age groups, black British ethnicities (compared with white people) and non-English speakers were more likely to express a lower inclination to get vaccinated if passports were introduced. While these groups comprise a relatively small proportion of the UK population, they cluster geographically and tend to be less inclined to get vaccinated in the first place.

Evidence that imposing vaccine passports could have the reverse behavioural effect from that intended by ministers will strengthen the hand of Tory backbenchers determined to see off the plan if it comes to a vote in the House of Commons.

Labour has also expressed concerns, suggesting a system that included Covid testing as an alternative to vaccination would be a better approach since fully jabbed individuals can still catch and pass on the virus.

Research into the behavioural effects of vaccine passports suggests the scheme triggers social division, said Prof John Drury, a participant in the Sage subcommittee advising on behavioural science, who was speaking in a personal capacity and not involved in the survey.

“Not only would vaccine passports create exclusion, that exclusion would be structured by existing inequalities. You only need to look at the data on who isn’t yet vaccinated to understand this – the young, the poor, ethnic minorities stand to be excluded.”

The negative impact of vaccine passports – once the underlying intention to get jabbed was accounted for in the survey – was disproportionately found in males and highly educated people. It’s unclear why that is, said de Figueiredo.

The study echoes historical data that suggests those who are already medically disfranchised will not be made more receptive to jabs by the introduction of more coercive measures, according to Caitjan Gainty, a senior lecturer in the history of science, technology and medicine at King’s College London, who was not involved in the survey study.

Another issue with vaccine passports, especially in light of the highly infectious Delta variant of coronavirus, is their weak scientific basis, scientists say. Someone who is double-jabbed is still half as likely to be infected as someone unvaccinated, notes Paul Hunter, professor of medicine at the University of East Anglia.

Many people will have been vaccinated to get their freedoms back, but with high rates of breakthrough infections it’s not impossible that freedoms could be taken away or made conditional on further doses, adds de Figueiredo. “This could be rather problematic as people may tire of this, may start refusing vaccines, and it’s not improbable that this rubs off on other vaccinations.”

Proposals for vaccine passports have been met with scepticism from Britain’s nightclub sector, which warns it could harm their recovery, while live music industry representatives expressed a preference for the current entry requirement for most venues and festivals – which allows the choice of providing proof of double-vaccination or recovery from Covid or a negative test.

Vaccine passport schemes introduced abroad have evolved in different directions and triggered varied reactions. In France, tens of thousands protested over a health pass allowing people to access restaurants, bars, planes and trains. The government this week extended the mandate to certain categories of staff.

Denmark’s “coronapas” system has been in operation since April but is being dropped from 10 September as authorities believe the virus is no longer a “critical threat” to society. Bars, cafes, restaurants, museums and tattooists have been open for anyone who can show a negative test result less than 72 hours old, or a completed vaccination, using a digital certificate.

Israel, which has been at the forefront of the jabs rollout, has had a “green pass” for much of the year. It released an app in February showing whether people have been fully vaccinated against Covid or have presumed immunity after contracting the disease.

A QR code system introduced last year in China categorised people into different colours, with green allowing them to move around freely if QR codes are requested in public spaces for entry.