The prospect of government changes to quarantine requirements when people are abroad on holiday have been condemned as “commercial catastrophic” for the outbound travel sector.

Additional complexity to existing post-lockdown travel regulations threatens to drive the “final nail in the coffin” of the industry.

The warning came from VIVID Travel boss Kane Pririe after the Department for Transport continued to exclude Portugal from the list of countries exempted from quarantine restrictions.

Travellers to England from Estonia, Latvia, Slovakia, Slovenia and St Vincent and the Grenadines will not have to self-isolate for 14 days from July 28 – bringing the list of “safe” countries up to 80.

However, the DfT also revealed it will update guidance weekly “to reflect the shifting international health picture”, meaning rules could change while people are away.

At the same time the Foreign Office added countries such as St Helena, St Maarten, St Martin and St Bathelemy, Aruba, Cambodia, Cook Islands, Cuba, Curacao, Falkland Islands, Fiji, Guadeloupe, New Caledonia, Samoa and Sri Lanka to a separate list of countries where advice is no longer against all-but-essential travel.

Pirie, owner and managing director of the long-haul specialist, said: “If the government has any interest in helping outbound travel companies and thousands of associated jobs survive they urgently need to reduce the complexity around the rules of engagement.

“Disjointed FCO travel advice for British nationals, four home nations tinkering with quarantining and overseas governments opening and closing borders is far too much already.

“The idea that rules on quarantining could change when you are away will be yet another list and final nail in the coffin. Commercially catastrophic and unnecessary.”

He added: “We are months into the crisis and it is time the government got its act together. We need a short but stable list of reciprocal arrangements where travel can flow.

“Quarantining should only be for the people who choose not to be tested on arrival. If Iceland can make that work then the UK can too.”