The outgoing prime minister will not receive any official papers during his week in Greece, his spokesperson said, just hours after a senior Tory claimed he would be “going through his red box”.
Mr Johnson is being criticised for taking a second holiday in August, but the spokesperson declined to say why he did not wait until after he leaves office on 5 September.
Meanwhile, two big removal vans were parked outside No 10, prompting speculation that the prime minister will depart with a large amount of furniture from his lavishly refurbished flat.
He is allowed to take any fittings that he paid for himself – although many were originally funded by a rich Tory donor – raising questions about the infamous £840-a-roll gold wallpaper.
The spokesperson was also unable to say whether Mr Johnson will return to Downing Street to live from next week, for the final fortnight of his premiership.
The second holiday was revealed when the prime minister was spotted with his wife Carrie in a supermarket in Nea Makri, a town to the east of Athens.
But the former Northern Ireland secretary, Brandon Lewis, denied he has “thrown in the towel” by heading abroad again, after an earlier break at a spa in Slovenia.
“I can assure you he will still be going through inboxes,” he told LBC Radio, adding: “Being out of the country does not mean the prime minister stops working.”
But Mr Johnson’s spokesperson revealed he would not receive any red boxes, saying: “If there are any urgent decisions that need to be made, he will of course take them.”
“He is contactable, as you would expect, but he is on leave,” he added, pointing to “national security” as an area where he would “obviously be kept informed”.
Dominic Raab, the deputy prime minister, would deputise at any meetings but, the spokesperson said, “as far as I’m aware there are no such meetings currently scheduled”.
Labour has accused Mr Johnson of treating his last weeks in power as “one big party”, despite the looming cost of living emergency from rocketing fuel bills.
Asked if Mr Johnson’s holiday could have waited a few weeks, his spokesperson said: “I can’t get into the decision around timings, but he is on leave this week. He will be back this weekend.”