People who are not fully-vaccinated will be barred from indoor events with crowds of 500 or more, under a ‘Plan B’ if there is a Covid surge this winter.

       Sajid Javid, the health secretary, confirmed the controversial “vaccine passports” plan – which he announced had been dropped last weekend – will be held in reserve.

       The first details of the move revealed it would be introduced for “indoor crowded settings with 500 or more attendees such as music venues or large receptions”, including all nightclubs.

       The events would be those where people “are likely to be in close proximity to people from other households”, a document set out.

       The vaccination rule would also be introduced for “outdoor, crowded settings with 4,000 or more attendees” and “any settings with 10,000 or more attendees, such as large sports and music stadia” – covering top football matches.

       But places of worship, wedding ceremonies, funerals and “other commemorative events” would be exempt, as would protests and “mass participation sporting events”.

       In a statement to MPs, Mr Javid declined to set out the exact “trigger” for moving to Plan B – but said it would be enacted if pressures on the NHS became “unsustainable”.

       Another “potential trigger” was the arrival of a “vaccine escape variant”, that would hit immunity from jabs, telling MPs: “No one can rule that out.”

       The other restrictions to be introduced would compulsory face coverings in crowded places – the rule ministers controversially axed in July – and guidance to work from home.

       Asked if MPs would be given a vote before any vaccine certification scheme was introduced, Mr Javid replied: “Of course.”

       The document states that ministers believe their existing plans – including vaccines for 12 to 15-year-olds and booster jabs for adults – “should be sufficient to reverse a resurgence in autumn or winter”.

       But it adds: “The government remains committed to taking whatever action is necessary to protect the NHS from being overwhelmed, but more harmful economic and social restrictions would only be considered as a last resort.”

       The Night Time Industries Association reacted with dismay to the announcement, saying its “rejoicing” of just a few days ago had been dashed.

       “Today, businesses up and down the country are once again thinking they may have to make an enormous and detrimental change to their operating model in the future, if infection rates increase,” said chief executive Michael Kill.

       Mr Javid, who had said Britons should not have “show your papers” to gain entry, played down the likelihood of a U-turn, saying: “If we keep making progress in the way we are, we won’t need any of those measures.”

       He also all-but confirmed that expensive day 2 PCR tests for travellers returning from abroad will be dropped – ahead of an expected announcement on Thursday – saying supporters of the move would be “pleased”.