NOT GIVING UP: Kate and Gerry McCann with a computer-generated image of how their missing daughter Madeleine might look now.

A girl spotted in Queenstown and thought to be Madeleine McCann is not the missing British child, police say.

Detectives had been investigating a New Year's Eve report from a Queenstown retailer who saw a man and a young fair-headed girl they thought bore a striking resemblance to Madeleine.

However, this morning, police said they had identified the girl and were 'absolutely satisfied' she was not the missing girl.

Reuters MISSING: Photo of Madeleine McCann, aged three, before she disappeared in 2007.

Detective Sergeant Brian Cameron did not give details of the Queenstown girl, other than to say it was not the first time people had confused the two girls and contacted police.

Three-year-old Madeleine went missing from the Ocean Club complex in Praia da Luz, Portugal, in 2007 while on holiday with her parents Kate and Gerry, and siblings Sean and Amelie.

The Queenstown retailer who reported the sighting said she immediately thought of Madeleine when the young blond-haired girl came into her store.

"She had the same eye defect as Madeleine. Only a very small percentage of the population have that and I was just staring at it the whole time to the point I forgot what they had purchased.

"As soon as they left, I looked up an image online to see which eye it was and it was the same eye," she said.

Madeleine has a blemish on her right eye called a coloboma of the iris. Figures suggest it occurs in about 0.007 per cent of the population.

The woman said neither the girl nor the dark-haired man she was with spoke while being served.

After the pair left her store, the woman alerted a passing police patrol.

"My only reason for alerting anybody is because if my little girl was missing and if someone on the other side of the world was seen who bore any considerable resemblance, I would want it ruled out."

Seventy police officers patrolling the Queenstown area on New Year's Eve were told to keep an eye out for the pair. Queenstown police contacted the Metropolitan police in Britain and the retailer also called the 24-hour Find Madeleine hotline.

It is not the first time a possible sighting of Madeleine has been reported in New Zealand. In December 2007, a CCTV video taken from The Warehouse in South Dunedin showed a girl who looked like the missing child being led into the store by a man. More than two years later, Dunedin police identified the girl and confirmed she was not Madeleine.

Last week, Kate McCann posted an update on the findmadeleine.com website thanking everyone who still held her daughter in their hearts and encouraged the public to continue to be vigilant.

"As Madeleine's parents, we won't be able to rest until we know that all that can be feasibly done to find her, and the person who took her, has been done."

"We are very aware that without public help it will be virtually impossible to find Madeleine."

In April, Scotland Yard released a photograph of her as she might look today as a 9-year-old.

At the time, the force also urged the Portuguese judiciary to reopen the case into Madeleine's disappearance.

Detective Chief Inspector Andy Redwood, who led a Metropolitan police review into the case, said he wanted the case reopened to establish what happened and ultimately to bring closure by solving the case.

"We genuinely believe there is a possibility she is alive," Redwood said.