More than 1500 people have phoned a police hotline to help trace British 4-year-old Madeleine McCann who was abducted in Portugal, the Association of Chief Police Officers has said.

Some of the information provided by the 1538 callers had been passed to the Portuguese investigation team. Madeleine went missing nearly a month ago from a holiday apartment in the Algarve as her parents dined in a nearby restaurant.

Police said dozens of holidaymakers at the Ocean Club Resort, at Praia da Luz, had also sent holiday photographs to a website set up as part of the appeal campaign.

They were encouraged to upload pictures of people not known to them who were snapped in the two weeks in the run-up to the toddler disappearing.

The pictures were enhanced, with the aid of new facial recognition software, to help build a picture of who was in the area at the time.

More than 170 people have sent 1000 photographs to the site, since its launch on May 21, ACPO said.

The McCanns have widened their appeal to Spain, where they believe their daughter may have been taken after her abduction on May 3.

The couple appealed for Spanish police to investigate actively the possibility that her disappearance may be linked to that of other children in Portugal and Spain.

The family received the backing of jockeys taking part in Saturday's Derby at Epsom, one of the country's biggest horse racing events of the year. Jockeys, including Frankie Dettori who will be riding the favourite Authorized, wore yellow ribbons in support of the campaign to find Madeleine.