The head of Portugal's police workers' union on Wednesday defended police in their efforts to find a kidnapped British girl, saying there are cases of missing children in Britain that are never found.

Portuguese police have faced criticism in British news media for being too slow and releasing too little information in their investigation of the disappearance of three-year-old Madeleine McCann from her bed in a resort in the Algarve last week.

"Children disappear in England that are never found," Armando Ferreira, president of the National Police Union, told news agency Lusa. "Portuguese police are making a great effort. I have colleagues volunteering during their days off to help."

Portuguese police have repeatedly stressed that unlike in Britain, they are obliged by law to keep all elements of the investigation secret and have given few clues to the media.

They have said they have followed up hundreds of leads and searched 500 apartments in and around the small Praia da Luz Algarve resort where Madeleine disappeared.

Britons in the area said they have been surprised by the low police presence.

"Back home in the UK the presence would be massive, you're only a mile away from where it happened and there's nothing going on," Andrew Forrester, a tourist from Wales who has volunteered to help in the search, told Reuters Television.

"It doesn't seem there's very much going on, it's just strange, very strange."

Portuguese President Anibal Cavaco Silva also defended the police, saying "we're doing everything to find the child alive."

Portugal's government said it had suspended an international campaign to promote the Algarve after the kidnapping.

The "Allgarve" campaign was set to begin next week with Chelsea football club manager Jose Mourinho promoting Portugal's sun-soaked beaches in the British media, but Economy Minister Manuel Pinho said it would be a "sensible move" to delay it.

"Portugal is one of the safest destinations in Europe and that image should remain that way," he told journalists in Lisbon, adding that he did not think Madeleine's disappearance would affect the flow of tourists to the Algarve.

About 11 million tourists flock to Portugal every year, and tourism accounts for up to 8 percent of gross domestic product, or more than 6 billion euros (4 billion pounds) a year.

Blond-haired Madeleine was snatched from her bed six days ago in the Ocean Club beach resort in the Algarve, yards from where her parents were dining.