The night that Madeleine McCann was abducted was not the first time that her parents had left her alone while on holiday, according to reports in Portugal.

The newspaper Correio da Manha says that the McCanns had left their children alone before during their holiday in the Algarve - a routine that, while normal at Praia da Luz, may have made it easy for her kidnapper to plan the abduction.

"Police have reconstructed the holiday routines of the McCanns and have come to the conclusion that the children were left alone on other occasions," the newspaper says.

It reported that throughout the week the McCanns and their friends made a habit of suppers by the pool while the children - Madeleine, her twin siblings, and three other children - slept alone in the apartments. The night she was abducted, Madeleine's parents had been checking on her roughly every half hour.

Kate McCann takes daughter Amelie to a creche this morning, while the search for Maddy continues

Statements to police from employees at the resort said that neither the McCanns nor other parents had demonstrated any worry about leaving the children alone. Employees also said this was normal behaviour at Praia da Luz.

The nightly routine, if observed by the kidnapper, would have made it easy to plan the kidnapping.

Last night two "Cracker-style" criminal behaviour experts from Britain flew into the Algarve to join investigators.

An appeal for help in the search has also gone out over the world wide web, with the Child Exploitation and Online Protection Centre issuing a statement in English, Portuguese, and Spanish. An e-poster with Madeleine's photo, reportedly created by her aunt Philomena McCann, is also circulating on the Internet.

A senior detective with experience of child abduction cases and a behavioural expert on paedophiles flew out after Portuguese authorities accepted an offer of help.

Portuguese detectives have no clear description of the suspect they are hunting over the disappearance of three-year-old Madeleine McCann.

The desperate state of the investigation was underlined today as it emerged that the e-fit had no facial features and lacked details of any sort.

Today one man who has been shown the portrait ridiculed its quality, describing it as "nothing more than an egg with a side parting".

Simon Russell, 40, revealed that officers even admitted the e-fit was useless.

Maddy: Missing for six days

The experts were called in as police in the UK privately declared astonishment at the "hopeless" Portuguese handling of the case.

The British ambassador to Portugal has defended the police search for Madeleine, who went missing from an Algarve holiday resort six days ago.

John Buck said he had been assured by the Portuguese authorities that "everything possible" was being done to ensure the girl's safe return.

His comments came after police said they had stepped up their efforts.

After visiting Madeleine's distraught parents Gerry and Kate, John Buck emerged to say that the couple appreciated the Portuguese efforts and said specialists from the two countries were working well together.

Mr Buck said: "This is, and must remain, a Portuguese police investigation.

"As you know, the Portuguese police operate under Portuguese law, and Portuguese law puts constraints on what they can say publicly and the information they can release."

He added: "I, and I know Kate and Gerry, with whom I've just been speaking for the past hour, are very grateful for their efforts."

Fireman search a shed in an abandoned farmhouse in the continuing search for Madeleine McCann

He also revealed he had been in touch with Portuguese cabinet ministers and the office of the Prime Minister.

Mr Buck, who has visited the couple repeatedly throughout their ordeal, said after his latest visit: "I wanted to assure myself personally that the necessary links between British and Portuguese experts here on the ground were working well, and they are."

It is six days since Madeleine, from Rothley in Leicestershire, was snatched as she slept in the family's Mark Warner holiday apartment in the Algarve resort of Praia da Luz.

Kate and Gerry McCann plead for information on missing Madeleine after a Mother's Day service on Sunday

Meanwhile, Mr and Mrs McCann have been left "in the dark", about the investigation, said a family friend. Jill Renwick said: "They know as much as any of us know."

In the family's home village of Rothley, near Leicester, Madeleine's great-uncle
Brian Kennedy said: "The family are holding up with difficulty. They are very frustrated with the lack of information."

Leicestershire Police has sent three liaison officers to help the McCanns, both 38, but it is understood that they too have been "banging their heads against brick walls" with their Portuguese counterparts.

They have not expressed their frustrations publicly for reasons of diplomacy, but a source said: "They have been putting questions on behalf of the family but getting zero response."

The family released a new statement on Wednesday afternoon, saying: "We are grateful to everyone searching for Madeleine. We are channeling our efforts into the search for her and continue to remain positive."

The family did not single out the police for their efforts.

The e-poster, reportedly created by Madeleine's aunt, circulating on the Internet today

Police in the UK have supplied detectives in the Algarve with a list of known child abusers who have moved to the region or are known to travel there.

Detectives in Leicestershire are also gathering statements from holidaymakers who were at the Mark Warner resort in Praia da Luz around the time Madeleine vanished and have now returned home.

Despite the McCanns' frustration, Portuguese police have repeatedly hidden behind a law which they say prevents them revealing any details and keeping even the family, let alone the media, fully informed of any developments.

In fact, though the Penal Process Code does silence them while an investigation is ongoing, there is a provision for the rule to be broken if the public is in danger, or if media reports need to be corrected.

Portuguese legal experts say there are grounds for using either or both exceptions to allow police fully to involve the press and public in the search.

Last night Portuguese police defended their operation, giving out details of their searches and revealing that 350 people have now called with suspicious sightings.

For the first time in five days, Chief Inspector Oligeario Sousa offered some concrete information, disclosing that 500 apartments had been searched, as well as ten miles of fields and rivers. He said 100 foreign nationals had been interviewed.