Portugal will co-operate with a new British police inquiry into the disappearance of Madeleine McCann, the Attorney-General's office in Lisbon said yesterday.

Scotland Yard said last week that it had identified potential suspects in the case and wanted to open a new international inquiry into Madeleine's abduction from a holiday apartment on the Algarve in 2007. But Britain has yet to deliver its formal request for assistance to the Portuguese authorities.

A spokesman for the Portuguese Attorney-General's office said that the country was a signatory to two European treaties on mutual legal assistance: "[Portugal] has an international obligation to cooperate in what concerns criminal investigations that require international cooperation, according with the conditions established by international instruments."

Madeleine was almost 4 when she vanished from her family's apartment in Praia da Luz in May 2007 while her parents dined with friends nearby.

The original police inquiry was inconclusive but the Metropolitan Police began a review two years ago. It wants to trace 38 "persons of interest" from five countries. Detectives said that neither Kate and Gerry McCann, Madeleine's parents, nor any of their friends, were on their list.