Private detectives hired by Madeleine McCann's parents have released an e-fit of a "Victoria Beckham lookalike" they believe may have information about the missing girl.

The woman was seen by two British men in Barcelona in Spain three days after the child went missing from Praia da Luz resort in Portugal.

She had a brief conversation with one of the men which suggested she might know something about what happened to Madeleine, the McCanns' investigators said.

Former detective inspector Dave Edgar, who is leading the McCanns' investigation, said it was possible that Madeleine could have been taken to Spain by sea from where she disappeared in the Algarve.

He told a press conference in central London yesterday: "Madeleine most definitely could have got from the area to Barcelona by yacht."

The British men, part of a larger group, saw the woman in the early hours of May 7, 2007, on a night out in Barcelona's popular Port Olimpic Marina.

The woman was well-dressed but appeared agitated and kept walking up and down outside the El Rey de la Gamba restaurant bar as if she was waiting to meet somebody.

When one of the British men approached and spoke to her, she said something that the McCanns' team described as "potentially significant to the investigation".

Mr Edgar refused to give any details, saying only: "She's a significant individual, I wouldn't describe her as a suspect."

After speaking to the witness, the woman – who is described as having an Australian accent – went into a bar next door and sat down on her own. While in the bar she had a heated conversation with a local in what seemed to be fluent Spanish.

The main witness, a married 41-year-old professional without children, contacted the McCanns' investigation team about six weeks ago.

Mr Edgar said that his delay in coming forward was for "personal reasons" but they were satisfied he was credible.

The woman was aged 30 to 35, slim, about 5ft 2ins with short brown hair.

The main witness also described her as "a bit of a Victoria Beckham lookalike".

Mr Edgar said the man had been drinking that night but was not drunk, and the woman was sober.

The McCanns' detectives travelled to Barcelona but all CCTV footage had been wiped.

Mr Edgar described the sighting as a ''strong lead" but, asked whether it was the strongest, replied: "I wouldn't say that."

Madeleine's parents, Kate and Gerry McCann, from Rothley, have been kept informed but spokesman Clarence Mitchell said: "They have learned through bitter experience not to get their hopes up or down."

Anyone who knows the woman should call 0845 8384699 or e-mail:

investigation@ findmadeleine.com.