Brits planning quarantine-free travel from the UK to mainland Europe or the USA have been warned not to expect trips before late July.
Paul Charles, chief executive of travel consultancy The PC Agency, warned that the reopening of travel has been "sacrificed by ministers watching their backs".
And the leading travel expert, who was among figures in the industry to express outrage when Portugal moved to the amber list last week, claims decisions are "highly political, not based on data at all".
People arriving in the UK from a green-tier country are not required to self-isolate, while amber arrivals must quarantine at home for 10 days.
There were hopes that destinations such as Spain, France, Italy and the US would be added to the green list ahead of the peak summer holiday season.
But The Liverpool Echo reports that Mr Charles believes his "clear understanding" of the issue means ministers "do not intend to open up travel to mainland Europe or the USA before the end of July".
He added: "Ministers have fallen into line to protect their future careers and potentially benefit from an upcoming Cabinet reshuffle.
"And that means sacrificing the early opening of the overseas travel sector.
"Now thousands of jobs are at risk - as are some airlines and travel firms - because June and July will be lost in travel terms."
Boris Johnson advised holidaymakers to follow the Government's "red, amber, green" guidance on foreign travel after being questioned about ministers' "contradictory" statements.
During a Downing Street press conference on Monday (June 14), the Prime Minister was asked what advice he recommended travellers to follow after earlier comments by Transport Secretary Grant Shapps and Environment Secretary George Eustice.
Mr Johnson said: "On travel abroad, I think that the most important thing is just to follow the red, amber, green guidance that we're giving.
"That's continually reviewed ... I wouldn't want to give any more guidance than that at this stage."
The Department for Transport is reviewing the travel lists every three weeks, which suggests the next changes will be announced on June 24.
