Dozens of sex offenders who travelled to the Algarve in the month before the disappearance of Madeleine McCann are being hunted by police in Portugal and Britain, The Times has learnt.

Portuguese detectives have drawn up a description of a British man whom they want to question over Madeleine’s disappearence. A computer-generated artist’s impression of the suspect shows a white man, 5ft 8in (1.7m) tall, aged 35 to 40, with short, dark hair.

In response, British detectives have compiled a list of every person on the sex offenders register who told police that they were travelling to the country.

The list was compiled by Leicestershire Constabulary over the weekend from records kept by every police force. Portuguese officers have also examined records at every hotel in Praia da Luz and the nearby town of Lagos to gather information on every visitor from the Midlands.

A Leicestershire Constabulary spokeswoman said: “We have received a number of calls from the public and police forces around the country with information relating to the disappearance of Madeleine McCann.”

Last night the Policia Judiciaria held another chaotic press conference at Portimão town hall. Chief Inspector Olegario Sousa, who is now heading the investigation, said that about 500 apartments at and around the holiday resort complex where Madeleine was abducted had been inspected. The search area now extends to about ten miles (16km) from the area.

Mr Sousa said: “Hundreds of people have been contacted, both Portuguese and foreign nationals, and more than 100 have been formally interviewed.” The officer appealed for understanding from the British public for the fact that, under Portuguese law, he was unable to provide more information.

Earlier he was unable to offer Madeleine’s family any assurance that she is still alive. “All the hours that have passed since her disappearance are against us and are against her too,” he said.

Last night Cristiano Ronaldo, the Manchester United and Portugal footballer, made a personal appeal for help. “I was very upset to hear of the abduction of Madeleine McCann and I appeal to anyone with information to please come forward,” he said.

Last night John Buck, the British Ambassador to Portugal, said that he had checked the progress of the investigation: “I have been in touch with Portuguese Cabinet ministers, the Prime Minister’s office and police. They all assure me everything is being done to ensure the safe return of Madeleine.”

Madeleine, from Rothley, near Leicester, disappeared last Thursday night after she was left with her younger twin brother and sister in a holiday apartment. Her parents, Gerry and Kate, were dining in a nearby restaurant and checking on them regularly.

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