UK police have written to the Portuguese authorities seeking help with the British inquiry into the disappearance of Madeleine McCann.

It is the second international letter of request to be made and comes amid reports that police are poised to make their first arrests.

According to the Daily Mirror, British police want to question three burglars who were operating in the Portuguese resort of Praia da Luz where Madeleine disappeared.

“The letter is a significant development,” a spokesman for Madeleine’s parents Kate and Gerry told the newspaper.

“It is necessary for British police to request the Portuguese authorities allow them to operate on their turf.

“It means they have the intention of arresting and interviewing X, Y or Z. We don’t know who they have their sights on but it’s likely it is the burglars.

“Whether the Portuguese will co-operate remains to be seen. It is a very sensitive issue with differences they have had.”

The Crown Prosecution Service and Scotland Yard have not commented on the detail of the latest letter to the Portuguese, apart from confirming it was sent last week.

Madeleine, who was then nearly four, disappeared from her family’s holiday apartment in Praia da Luz in the Algarve on May 3, 2007 as her parents dined at a nearby restaurant with friends.

British detectives launched a fresh investigation into the youngster’s disappearance in July last year – two years into a review of the case – and made renewed appeals on television in the UK, the Netherlands and Germany.

After shelving their inquiry into Madeleine’s disappearance in 2008, Portuguese authorities said last October that a review had uncovered enough new information to justify reopening it.