Around 100 people are trying to enter the country each day with a “fake Covid certificate”, MPs have heard.

The fake documents claiming a traveller has a recent negative test result are “very easy” to forge, MPs were told.

And there is no way to tell how many more are being missed.

We do get 100 or more a day of fake Covid certificates, that we catch.

Lucy Moreton, professional officer for the Immigration Services Union (ISU), which represents border immigration and customs staff in the UK, also said there is “little to no” evidence on how well people are adhering to quarantine rules.

Meanwhile, MPs heard that long queues found at airports could be a “breeding ground” for the virus.

And experts raised concerns about the traffic light system for travel.

Ms Moreton told the All Party Parliamentary Group on Coronavirus that around 20,000 people are coming into the country each day, the majority of whom are hauliers.

To enter England people must provide proof of a negative test taken in the three days before departure – which can be shown to border agents as a printed document or through an email or text message.

Asked how border agents are able to verify proof of a negative test, Ms Moreton told MPs: “We’re not is the simple answer, it’s predominately taken on trust.

“We do get 100 or more a day of fake Covid certificates, that we catch.”

Europol warned earlier this year about the illicit sale of false negative Covid test certificates.

This included a forgery ring selling negative test results to passengers at Charles de Gaulle Airport in Paris, and in the UK fraudsters were caught selling bogus Covid-19 documents showing negative test results for £100 each.

“We catch them if there is a spelling error somewhere,” Ms Moreton said.

But many certificates are in a foreign language which could make spelling mistakes trickier to spot, she added

“Otherwise they are taken at face value,” she added.

She said that the documents are checked against a series of code numbers but “these things are very easy to knock up electronically unfortunately”.

Asked how many could be falling through the cracks, she added: “It’s inherently unknowable.

“A lot of the border and immigration and migration and quarantine controls are based on trust: we trust people when they say they have not been in a red list country in the last 10 days; we trust people when they say that they are going to 2 Acacia Avenue to quarantine; we trust that there is an Acacia Avenue and that when they are going to go there, they are going to stay there.

“The whole thing is based on an assumption that people will do the right thing.”

Ms Moreton said that it was not possible to segregate people depending on which country they had come from in immigration halls – where people are waiting an average of two to three hours while border agents check their usual travel documentation as well as additional requirements as a result of the pandemic.

Asked if the process itself is a “breeding ground for infections”, she said: “Right now, very much so. When it’s so slow and the queues are so bad, then it is a risk both to our members and the travellers in those queues.”

Ms Moreton added: “If you have got someone arriving from a country where you don’t have to go into a hotel quarantine, who has managed to catch the virus from someone who does, you may have isolated the person… but the person who bumped shoulders with them in the airport who has just vanished off into the wide blue yonder, you’ve no way of knowing who that is.”

She said that queues in immigration halls vary, but on average there are two to three hour delays at large locations like Heathrow.

Deenan Pillay, professor of virology at University College London, told MPs that the queues in airports “makes a nonsense of things”.

“When I see pictures of Heathrow Airport in the immigration hall, indoors, people queuing for hours and hours and then going off to their amber or red quarantine – it makes a nonsense of things,” he said.

Meanwhile, Dr Gabriel Scally, visiting professor of public health at the University of Bristol and a member of the Independent Sage committee, raised concerns about the forthcoming holiday season, saying that holiday destinations could be “international mixing pots”.

He told the group of parliamentarians: “I don’t believe in reds and greens – I believe in quarantine or not quarantine.

“There is no such thing as a half quarantine – you can’t do it by half you either do it properly, or don’t bother doing this at all, which of course has been the UK’s position for far, far too long.

“We don’t know necessarily where someone starts their journey we don’t know where they transmitted, we don’t know what transport they have used to get to and from particular places.

“And I think this is a particular problem in a holiday season, as we’re heading into … which will be an international mixing pot, almost by definition.

“So, whether a country is green or red to me as a public health doctor, I’m not interested in that – I’m interested in managing the isolation of people arriving from abroad at this time.”

None of the experts quizzed by MPs said they would be prepared to embark on international travel at this time.

After the session, Layla Moran, chair of the APPG on Coronavirus, said: “The stark evidence we heard today exposed how current border checks are totally inadequate to stop Covid cases entering the UK, including dangerous variants.

“The Government must act now to stop our airports becoming breeding grounds for the virus.

“That means reducing overcrowding in arrival halls, effectively separating passengers arriving from red list countries and carrying out thorough checks to root out fake documentation and ensure people comply with the rules.

“The Government should be actively discouraging foreign travel and be transparent about the risks it carries, rather than using up a traffic light system that gives a false sense of security.”