The search for Madeleine McCann was focused on Australia today after police there said a woman came forward claiming to know someone being sought by private detectives.

Investigators for the family want to trace a Victoria Beckham lookalike who asked a witness at a Spanish marina if he was there to deliver her "new daughter", just days after the little girl's disappearance.

The well-dressed woman was described as possibly having an Australian accent and appeared agitated.

A New South Wales Police Force spokesman said: "Detectives received information about a woman who is similar in description to the woman being sought by private investigators examining the disappearance of Madeleine McCann.

"This afternoon, a Sydney woman provided a formal statement to detectives at a Sydney police station. She claims to know the identity of the woman being sought by the private investigators attached to the McCann family.

"New South Wales Police Force will forward the information received to the Australian Federal Police for follow up."

The McCann family's private detectives are following up more than 600 calls and e-mails, including many which investigators describe as "viable leads", spokesman Clarence Mitchell said yesterday.

Asked about reported attempts to trace a motor boat said to have been in the marina in Barcelona at around the time the woman was sighted, he said: "The investigators will follow the evidence wherever it takes them. Vessel movements are just one area of the inquiry."

According to national newspaper reports, a yacht called Willpower, belonging to multi-millionaire socialite Rhonda Wyllie, was moored in Barcelona, three days after Madeleine disappeared from a holiday resort in Portugal in May, 2007.

Private detectives working for Madeleine's parents want to speak with Mrs Wyllie and her daughter, Melissa Karlson, 31, to find out why the vessel was in Barcelona and if either woman was travelling aboard.

Mr Mitchell added that many callers had passed information directly to the police in Australia and that he was aware of reports that a woman in Sydney had given police a formal statement saying she knew the identity of the woman.

"The information received, including the reported statement from a woman in New South Wales, is being passed on to investigators and we will be in touch with the Federal Police (in Australia)," he said.

In an interview with Australia's Nine Network, Mr Mitchell said: "We have had dozens of names for the woman we're looking for given to us ... and out of that, the detectives have a number of viable leads."

Madeleine was three when she went missing from her family's holiday apartment in Praia da Luz, in the Algarve, on May 3, 2007. Just over 72 hours later, two British men saw the woman being sought while on a night out in the Port Olimpic Marina in Barcelona.