The search for Madeleine McCann is now focused on Australia 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 spokesman for the New South Wales Police Force said yesterday: “Detectives have received information about a woman who is similar in description of the woman being sought by private investigators examining the disappearance of British child 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.”

The McCann family's private detectives are following up more than 600 calls and emails, 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 current inquiry.”

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

Madeleine was nearly four when she went missing from her family's holiday apartment in Praia da Luz in the Algarve on May 3, 2007 while her parents dined with friends nearby.

Just over 72 hours later, in the early hours of May 7, two British men saw the woman being sought while on a night out in the popular Port Olimpic Marina in Barcelona.

After speaking to one of the witnesses the woman went into a bar next door, where she had a heated conversation with a local in what seemed to be fluent Spanish.