Later today the home secretary, Priti Patel, will give MPs more details of plans for mandatory self-isolation for arrivals in the UK from 8 June.
The 14-day quarantine measures will effectively kill off outbound and inbound tourism for as long as they prevail.
Grant Shapps, the transport secretary, has promoted “air bridge” arrangements with key destinations to limit the damage to airlines, holiday companies and UK tourism businesses.
These bilateral deals could be in place by 29 June, when the quarantine policy comes up for renewal.
Portugal, which has a rate of coronavirus infections comparable with the UK, stands to be severely affected by the quarantine policy. Around half of its overseas visitors are British, compared with 22 per cent for Spain.
The country is expecting to be fully open for tourists by 1 July – with special rules, including Covid-19 tests on arrival, for the island of Madeira.
The foreign minister, Augusto Santos Silva, described quarantine as “an enemy of tourism”.
He told the BBC that an “air bridge” agreement between the UK and Portugal is being negotiated, saying: “We are already contacting in order to see if the quarantine that was imposed by the UK until the end of June can not be prolonged to the end of July and August.
“You can come to us this summer. We are preparing to receive you in the safest conditions.”
The revelation comes as countries across Europe are opening up. Italy has opened its borders and is now allowing unrestricted travel nationwide.
Germany is cautioning its citizens against visiting the UK, but says that British visitors are among many European nationalities who can now visit the country.