Covid passports could be used in pubs, bars and restaurants as new government guidance for businesses urged their wider rollout.
On Wednesday, ministers published delayed advice for businesses on how to operate when the country moves to step four of the roadmap out of lockdown on Monday.
It said hospitality firms will be encouraged to consider asking customers to show Covid passports to enter their premises.
The Government was accused of widening the net of companies encouraged to use domestic Covid passports after Boris Johnson signalled on Monday that they would be recommended for nightclubs and venues with "large crowds".
The Prime Minister said relevant firms should show "social responsibility" and make use of the NHS Covid pass app, which shows proof of double vaccination, a recent negative test or natural immunity, as "a means of entry".
The updated guidance sparked a backlash among Conservative MPs and hospitality chiefs after advice specifically for restaurants, pubs, bars, nightclubs and takeaway services encouraged the use of Covid passports.
The document stated: "Consider the use of the NHS Covid pass to reduce the risk of transmission at your venue or event."
It went on to say the Government would "work with organisations that operate large, crowded settings (for example, nightclubs) where people are likely to be in close proximity to a large number of those from other households to use the NHS Covid pass as a condition of entry".
Steve Baker, the deputy chairman of the Covid Recovery Group of lockdown-sceptic Tories, said: "I am simply astonished that, after everything the Prime Minister and Michael Gove said in the past about ID cards, they are advancing this fast down this really quite appalling path."
He told The Telegraph that an "ever greater circle of businesses" were being netted by the guidance and added: "I can only hope it can be changed as soon as feasible."
Kate Nicholls, the chief executive of the industry body UKHospitality, said the guidance for pubs and restaurants was "disappointing" in the wake of a select committee of MPs and a Cabinet Office consultation "acknowledging that this was a very difficult thing to implement in a domestic hospitality setting".
She said ministers needed to provide a "whole suite of guidance" to explain how Covid passports should work in the sector "for us to decide whether we are willing to adopt this on a voluntary basis".
Predicting that few businesses would adopt the measure by Monday, from when the guidance is meant to apply, she said: "I don’t think anybody would be able to introduce this on a voluntary basis from Monday until we have clarification."
Ms Nicholls added that "more work is needed by the Government", warning that there were "real concerns" around equalities legislation, and "practical issues" around the type of testing that qualifies and how businesses should handle customers’ personal health data.
The pace of the UK’s vaccination roll-out is slowing
The updated government Covid guidance for businesses also encourages shops and offices to keep masks, while the continued use of table service is also recommended for hospitality venues.
It comes amid fears that retaining optional measures after legal requirements are scrapped could dent consumer confidence and stifle the economic recovery.
The fresh guidance for shops said they will be expected to ask customers to continue to wear "a face covering in crowded, enclosed spaces", while staff should also be encouraged to use them in indoors areas.
A study has found that hospitality and shop workers could be driving the third wave of virus infections as they are 20 per cent less likely to have been vaccinated.
Helen Ward, a professor of public health at Imperial College London, said healthcare workers were 10 times more likely, and care workers four times more likely, to have been vaccinated than non-key workers.
She added: "We also found that in some other public-facing occupations such as hospitality and retail, there was 20 per cent lower coverage of vaccine."