Boris Johnson today defied a huge Tory backlash to insist coronavirus testing at airports would only give a 'false sense of security'.
MPs voiced frustration as Mr Johnson again poured cold water on the idea, despite desperate pleas to prevent the 'demise' of the aviation sector.
The premier said Public Health England believed only 7 per cent of cases could be caught by screening people on arrival. Speaking during a visit to a HS2 site in Solihull, he said he understood the 'difficulties' faced by air industry but quarantine remained 'vital'.
A No10 spokesman added: 'Testing at the border does not work to catch people who may go on to get the virus.'
But Conservative MP Henry Smith, who chairs the all-party group on aviation, pointed out that other major countries such as Germany and France were already introducing testing at airports. He said the government could not allow the UK to be at a 'competitive disadvantage'.
A growing band of Tory rebels are hoping that airport testing could be the next in a string of government policy U-turns. In a potential chink of light, Grant Shapps today admitted that the move could halve the 14-day quarantine period.
While he stressed routine screening was not a 'silver bullet', Mr Shapps suggested that it could be a way of reducing the restrictions on travellers from higher-infection countries.
The comments came as the Cabinet minister conceded that the government's quarantine rules are causing 'confusion', after England kept Portugal on the safe list - despite Scotland and Wales imposing curbs.
Amid rising anger from bewildered holidaymakers that the system amounts to 'roulette', the he said starkly different approaches within the UK were a problem.
But he insisted that the Westminster government had assessed the best evidence and concluded that Portugal was still low-risk, and swiped at Scotland for decreeing that travellers from Greece must self-isolate this week before even seeing the latest data.
On a visit to an HS2 site in Solihull today, Boris Johnson said Public Health England believed only 7 per cent of cases could be caught by screening people on arrival at airports
Mr Johnson warned that testing at airports could give people a 'false sense of confidence'
The UK's key metric for introducing quarantine is how many cases a country has had in total over the past week, adjusted to per 100,000 of population. Spain and France are still well above the level, while Portugal has also crept over it
Portugal has been above the trigger threshold for UK quarantine measures for the past few days - but Grant Shapps said they were also looking at the proportion of tests that come back positive, and that had fallen
Scotland and Wales have imposed restrictions on Greece, even though the case rates are still relatively low
An exclusive poll for MailOnline by Redfield & Wilton Strategies found just 24 per cent believe the quarantine system is working, while 48 per cent say it is not
Grant Shapps sparked a bitter row with Scotland and Wales today after accusing them of quarantining Portugal and Greece because they had not inspected the data closely enough.
Amid rising anger from bewildered holidaymakers that the system amounts to 'roulette', the Transport Secretary conceded that starkly different approaches within the UK were 'confusing'.
But he insisted that the Westminster government had assessed the best evidence and concluded that Portugal was still low-risk, and swiped at Scotland for decreeing that travellers from Greece must self-isolate this week before even seeing the latest data. He said Welsh minister might not have 'noticed' that the proportion of tests coming back positive in Portugal had fallen.
However, the Scottish government lashed back by accusing Mr Shapps of 'jumping the gun' by announcing a decision before the nations had discussed the situation.
Mr Shapps also hinted that the government could take a more regional approach in future, and admitted that airport testing - demanded by many to save the aviation industry - could cut the 14-day quarantine period in half.
The desperate defence came amid growing evidence that the public is losing patience with the regime. An exclusive poll for MailOnline by Redfield & Wilton Strategies found just 24 per cent believe it is working, while 48 per cent say it is not.
Around a third want more countries added to the list of exempt countries.
Mr Johnson said quarantine measures for arrivals from countries deemed high-risk must remain 'a vital part' of the fight against coronavirus.
Asked during a visit to Solihull, he said he understands 'the difficulties' the airline industry is going through but said testing at points of entry only identifies 7 per cent of the cases.
'So 93 per cent of the time you could have a real false sense of security, a false sense of confidence when you arrive and take a test,' he said.
'That's why the quarantine system that we have has got to be an important part of our repertoire, of our toolbox, in fighting Covid.
'What we don't want to see is reinfection coming in from abroad and quarantine is a vital part of that.'
Mr Smith said testing had to be part of the solution to easing quarantine. 'Countries like Germany, France quite a few others are testing,' he said.
'We are at a competitive disadvantage. Testing also means there is greater confidence for people to travel, and also greater confidence in terms of public health.
'I think it is the answer. I am a little bit frustrated that the government don't seem to be there yet,'
He added: 'It seems to be effective. Obviously nothing is foolproof.'
Mr Smith said Heathrow had suggested a two-test process with a five-day quarantine.
Challenged on the demands for airports testing from across the industry, Mr Shapps told Sky News: 'I know that airport testing is one of those things that sounds so logical. You come in, you get a test, perhaps one of these very quick test and you are free not to quarantine,' he said.
'The problem we have, and this is what I am working with airports on at the moment, and the industry, is that a day zero test as you get home is unlikely to find the vast majority of people who have travelled with coronavirus but are asymptomatic…
'There are arguments about this, but PHE say that would perhaps pick up just seven per cent of people who are in fact positive, and allow those people to sort of go off.
'So you probably have to have some kind of quarantine period in here, perhaps seven or eight days, maybe a test then.
'But these are the things that we are working through at the moment.'
During his round of interviews, Mr Shapps said there was an 'argument' for judging islands separately from mainland countries. 'I think there is an argument for regionalising it… but having said that… actually the islands (in Spain) now wouldn't be fine.
'But it is fluid and I do accept there is space to look at those types of things.'
Virgin Atlantic has confirmed it could axe a further 1,150 jobs from across the company taking the total number of job losses to 4,700 during the coronavirus crisis.
The company has said they are 'working closely with unions Unite and BALPA' and that a company-wide consultation period of 45 days begins today.
It comes less than four months after axing 3,150 roles and announcing