The warning follows new allegations that have surfaced in the Portuguese press. One newspaper has alleged that tests on evidence carried out in the UK suggest that the four-year-old and twins Sean and Amelie were given the drugs on May 3.
A spokesman for the couple said the allegations were "hurtful" and he would be monitoring how the claims were covered in Britain. Spokesman Clarence Mitchell said: "Contrary to renewed speculation in the Portuguese press, Gerry and Kate McCann wish to make it categorically clear that they have never, ever used sedatives on their children. To suggest otherwise is as outrageous as it is hurtful.Lawyers for the McCanns will be monitoring British coverage of the latest Portuguese claims very closely and will take action if it's felt necessary."