The panel said there were "numerous issues that remain problematic" with the rule requiring athletes to give detailed schedules of their whereabouts for drug testing.

It has angered many individuals, including Britain's top tennis player Andy Murray, and sports organisations and has led to legal challenges.

The panel said: "Care should be taken to avoid the false belief that it ensures, throughout the world, an adequate level of protection for personal data processed in the EU, as required by EU law.

"It is also in light of the proportionality principle that the Working Party invites WADA and anti-doping organisations to reassess the collection of whereabouts as it is conceived today, and more in general, the current retention period of processed data."

The panel's decision will form the basis of a broader and far-reaching binding legal opinion by the European Commission, the executive arm which oversees EU legislation within the 27-nation bloc due to be published before the summer.

EU Sports Commissioner Jan Figel had asked WADA to suspend the rule, in force since January 1, while Brussels examined it.

John Fahey, the President of WADA, said: "WADA repeatedly offered to meet with the Working Party to provide more information and clarifications, but the European Commission, acting as the Working Party Secretariat, regrettably turned down our requests.

"By challenging well-established and accepted anti-doping practices and offering no constructive solutions, the Working Party could potentially undermine the fight against doping in sport, and the protections offered to clean athletes in the region of the world [Europe] that has previously been a leader in this fight."

Many top athletes such as tennis world number one Rafa Nadal and Olympic pole vault champion Yelena Isinbayeva say they oppose the policy under which athletes have to give three months' notice of where they will be for an hour each day.

The panel said: "WADA should reconsider requesting the residence on each day of the following quarter [even temporary lodging] as this would appear to be questionable."

The International Olympic Committee (IOC) supports the rule but WADA is at loggerheads with many sports governing bodies such as soccer's FIFA and cycling's UCI over the matter.

A legal challenge has been lodged in Belgium on behalf of 65 athletes, including cyclists and volleyball players, who argue the rule breaks EU privacy laws.

FIFPro, the soccer players' union, is also mounting a case.

FIFA also say out-of-competition tests should take place only at club training facilities and players should not be tested during holidays in order to respect their private lives.

The EU panel said "controls should be carried out at appropriate times and by appropriate methods without unreasonably interfering with the private life of a sportsman or sportswoman."

The opinion stated that the "type of sport" and "level at which the athlete competes" should also be taken into account before testing.