Tui faces legal action from more than 400 holidaymakers after suffering from “crippling sickness” in Mexico.
The operator is reportedly being accused of failing to pass on public health warnings to travellers about cyclospora – a bug that causes severe vomiting and diarrhoea.
Holidaymakers blamed the sickness bug for ruining their trips, which included honeymoons.
The Sunday Times reported that at one hotel, the Grand Sirenis Resort and Spa south of Cancun, almost 200 Tui customers became extremely sick in 2016 with symptoms similar to cyclospora.
Many other hotels were affected, including the Sensatori Resort in Riviera Maya with 95 victims.
Operators were reported to have been told by Abta in July and August 2016 that people should be notified before travelling to Mexico about the outbreak of cyclospora.
However, Simpson Millar, a law firm representing the tourists, claimed that none of its clients were told about the dangerous parasite in advance of travel.
Other holidaymakers claimed they were handed a warning letter only after they arrived in Mexico.
Nick Harris, head of travel law at Simpson Millar, who is taking the class action through Manchester county court, said the failure to alert tourists to the health warning was wrong.
“This would have given customers an opportunity to cancel and get a refund, or book a different holiday,” he said. “Many of my clients were only told about this horrible infection once they arrived.
“People had no chance to get their money back and choose another destination.”
Tui said it would be inappropriate to comment on ongoing legal proceedings, adding: “It is important to note that the number of customers who reported any sickness during their stay make up less than one per cent of the total customers who stayed in these resorts during the ten-month period.”
The newspaper said Abta refused to comment.
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