Adrian Goldthorpe, 68, from Leeds, and fellow passengers from a plane he had travelled on were informed on Friday that one of the Vietnamese cabin crew had tested positive for coronavirus.
The group were initially told to self isolate in their room, Mr Goldthorpe said, although he received a phone call about six hours later to say the police were on their way to collect passengers who had been on the plane.
He alleged that he was given just minutes to pack before three officials in protective clothing escorted the group via minibus to Cua Dai Beach in Hoi An - described by Mr Goldthorpe as a disused school.
When the group arrived, Mr Goldthorpe said the conditions were “filthy” - with only metal bunk beds with mosquito nets provided.
Mr Goldthorpe, who flew into Vietnam on March 8, told The Yorkshire Post: “There are filthy toilets and only a cold tap. We were given water. There are no showers, we used a hose pipe outside.”
Mr Goldthorpe was tested for coronavirus on March 14 and is awaiting results at the time of writing.
In a letter addressed to the MP for Elmet and Rothwell, Alec Sherbrooke, Mr Goldthorpe said: “We now have one toilet and a cold tap between 27 people, including a young baby.
“We are all well and have had normal temperatures recorded this morning. We are asking for urgent UK government assistance to repatriate us.
“We are extremely concerned for our safety. There is also a real concern about our mental well-being, our party included two young independent travellers.”
Mr Goldthorpe and the fellow passengers are now awaiting the results of the coronavirus tests.
They face at least another week in the conditions, with quarantine due to end on March 22 at the earliest to ensure 14 days of no contact.
Mr Goldthorpe said none of the party had shown any symptoms of the virus and he felt “OK”.
The Foreign and Commonwealth Office has been contacted for comment.