But a spokeswoman for Leicestershire Constabulary would not confirm whether Supt Prior had issued such an appeal. She also would not say if there had been any attempt to interview former guests.
Supt Prior is said to have told tourists in the letter: "I have now been asked by the Portuguese investigation team to arrange for DNA samples and fingerprints to be taken from holidaymakers living in the UK who were staying at the Ocean Club Resort." He goes on to emphasise that the request is "routine practice", the newspaper reported.
The development comes a month after Kate and Gerry McCann were named as suspects over the disappearance of their daughter.