The woman who reported a possible sighting of Madeleine McCann in New Zealand  which was kept secret by Portuguese police said today she 'absolutely believes' it was the missing girl.

Files have been released showing that Portuguese police dismissed dozens of potential sightings of Madeleine.

Leads from around the world - including the CCTV footage from New Zealand of a child looking strikingly like the missing girl - were filed away under the heading 'not relevant'.

Information that police forces in the United States, Europe and North Africa considered important was also discarded.

None of the files was handed to private investigators working for Madeleine's parents, Gerry and Kate.

Lead: This CCTV image of a girl strongly resembling Madeleine in a supermarket in New Zealand was among the leads deemed 'not relevant' by Portugese police

Taryn Dryfhout was working on the tills at the Warehouse discount store in Dunedin, New Zealand, when she saw the girl with a man, a woman and a boy.

She said the girl 'looked just like" Madeleine and spoke with an English accent.

Ms Dryfhout told broadcaster TVNZ's ONE News: 'She told me that her name was Hayley and was quite apprehensive... and sort of stammered over her words when she was trying to think of her name. She was just very shy and afraid.'

The shop worker said the adults with the children were 'a little bit suspicious' and added that the woman seemed to be in a hurry to leave when she spoke to her.

Ms Dryfhout said it was disappointing that her possible sighting was not fully followed up.

She told the broadcaster: 'I absolutely believe it was her. I have no doubt in my mind'.

Mrs McCann, 41, said the disclosure of the secret files was heartbreaking and shocking.

Their existence came to light in a legal action brought by the McCanns against Goncalo Amaral, the disgraced detective who was in charge of the case.

No follow up: Another CCTV image showing the girl resembling Maddie in the New Zealand supermarket

They had wanted to stop him airing the slur that they had been involved in their daughter's disappearance.

The leads were all received and archived after Algarve police closed the case in July 2008.

Madeleine was four when she vanished from the family's holiday apartment in Praia da Luz in May 2007. Her parents were at a restaurant 80 yards away.

They now have a copy of the 2,000-page dossier which was published yesterday on the order of a court in Portugal after an application by newspapers including the Daily Mail.

The McCanns are incensed that their private investigators were given no access to the sightings at the time.

Madeleine went missing from Praia da Luz in Portugal in May 2007

Mrs McCann said: 'There are instances where information which we think is very credible and worthy of information has not been actioned.

'We're gutted, it's absolutely shocking and difficult. Some of the information handed in was very credible. It's heartbreaking to know that it seems to end there.'

Mr McCann, also 41, was particularly angered at Inspector Ricardo Paiva, who was responsible for collating any information about Madeleine after the formal investigation ended.

He said: 'Inspector Paiva believes Madeleine is dead. How can he investigate thoroughly if he believes that? We know now there is a lot of information just filed away - and that is not acceptable. Once the file has been closed, what has actually been done? Next to nothing.'

The file contains a series of sightings which the McCanns would have expected to be fully investigated.

The astonishing CCTV footage from New Zealand shows a girl very like Madeleine being led into a supermarket by a portly man in shorts - seven months after her disappearance.

The man's behaviour aroused the suspicions of a female security guard in the shop in Dunedin on the South Island and she approached the girl to establish she was British.

Although the girl said her name was 'Hailey', the security guard was convinced the girl was Madeleine and reported the incident to police.

Kate and Gerry McCann said they were 'gutted' to discover that they weren't given access to secret files involving their daughter's disappearance

Other discarded leads include:

•    A British ex-pat saying he saw a girl being dragged along a road toward the airport on the night Madeleine disappeared. He had not approached the authorities earlier because he was wanted for fraud.

•     A girl like Madeleine was seen with an unkempt Spanish-looking man in his 30s at a shop near Murcia. The woman witness followed the girl but the pair vanished. She failed to tell Spanish police until June 2008.

Secret files: The police dossier

•     Another lookalike wearing only a dirty yellow jumper was seen being held at gunpoint on a French motorway by a half-naked man in August 2008. French lorry driver Michel Guidard walked toward them only to be threatened with a gun.

•    Photos from the internet uncovered by a female French detective were found to show images of sexual abuse which involved a girl resembling Madeleine.

•     An account by a Scottish mother of two who saw a girl who looked like Madeleine with a group of gipsies in Albufeira, Portugal, in July 2008. A woman who was with the girl ran off down the hill with her when two police officers turned up.

•    Details of a sighting of a girl on October 9, 2008, with a Portuguese man living in the U.S. He allegedly ran a child trafficking operation smuggling in children from his homeland, Mexico and Greece.

Clarence Mitchell, spokesman for the McCanns, said: 'They are incredibly frustrated that this was sitting there and being disregarded by the Portuguese police.

'They were shocked when they saw the scale of the information that had come in and the lack of action taken.

'There are potential leads in the file that are now being followed up by our investigators.

'It's more than a pity that the file has just sat there for so long and simply marked "not relevant" by the Portuguese.

'There are also images in the file that are strikingly similar to Madeleine and are being looked into.'