People returning to England from abroad could face longer peak-time airport queues because of Covid document checks, a union has warned.
The Immigration Services Union said looking at details of jabs, tests and possible virus exposure made processing passengers three to four times slower.
Fully jabbed UK citizens returning to England from amber list countries will not need to quarantine from 19 July.
The government admitted travel would be more disrupted than pre-pandemic.
But Transport Secretary Grant Shapps added that most of the document processing would happen at check-ins rather than at Border Force points – and airports, airlines and train and ferry companies were developing apps to speed this up.
On Thursday, the government announced that fully vaccinated UK residents returning to England from amber list travel destinations – which include popular holiday countries Spain, France, Italy and the US – would no longer have to quarantine from Monday 19 July.
But they will have to complete several documents. One of these is a passenger locator form – monitoring possible contact with people who have coronavirus – to be submitted at least 48 hours in advance.
Travellers will still need to pay for a Covid test three days before returning to England, and a PCR test two days after arriving, as well as show proof they were fully vaccinated at least 14 days previously.
Northern Ireland plans to adopt the same changes from 26 July, while both Scotland and Wales have said they will consider whether to follow the same rules.
Airlines and travel agents have reported a surge in bookings for overseas holidays since England’s new rules were announced.
Lucy Moreton, the Immigration Services Union’s professional officer, told BBC Radio 4’s Today programme the government needed to recruit more Border Force workers to cope with the increased demand.
She said social distancing within airports and Covid self-isolation were worsening passenger processing backlogs caused by longer-standing staff shortages.
“At the moment we are seeing peak-time queues somewhere in the one-to-two-hour mark, where we have got several aircraft that arrive at the same time,” Ms Moreton added.
“Exactly how long you are going to have to wait depends on where you are flying into, how many other people are flying at the same time and also how ready the other passengers around you and in other aircraft are.”
She added: “It takes about three to four times longer to check somebody’s Covid documentation than it would to check them for border purposes.”
Ordinary border checks took two to four minutes per person, Ms Moreton said, adding that those involving all four documents would amount to eight to 12 minutes.
Some airports incorporated these at their e-gates – automated passport barriers – “but not all of them are available everywhere”, she said.
Also speaking to Today, Mr Shapps admitted travel would “be more disrupted than it was back in 2019”, but the issue was “going to be on the check-in side rather than the border side” at Heathrow and elsewhere.
Airlines and train and ferry companies were “looking at digitising a lot of that”, he said, adding: “That could help, but undeniably this is more disruptive than in years gone by.”