Those affected travelled to the resort in Hurghada between February and July this year and booked through the tour operator.
All complained of gastric symptoms, including diarrhoea, vomiting and lethargy. One holidaymaker from Cardiff was diagnosed with a bacterial infection by the hotel doctor, while a Hampshire lorry driver was put on a drip during his stay.
More than 15 of those who fell ill have now instructed serious injury lawyers at Irwin Mitchell to investigate. The firm has successfully represented holidaymakers returning from the Jaz Aquamarine Hotel in 2016, 2017, 2018.
Irwin Mitchell solicitor Hannah Clifford said: "To hear what our clients have been through while at this resort is deeply concerning. They had saved for a long time and had been looking forward to their holidays, which were ruined when they fell ill.
"Gastric symptoms should never be downplayed as they can lead to long-term health issues, and this is not something you expect to be struck down with at a five-star hotel."
A Tui spokesperson said: "We are sorry to hear of these experiences at the Jaz Aquamarine Hotel. As this is now a legal matter, it would be inappropriate to comment further at this time. We’d like to reassure customers that we regularly audit all of our hotels in respect to health and safety, including hygiene."