Efforts to find Madeleine McCann by British police have been branded "absurd" by a top Portuguese politician.

Metropolitan Police officers have been accused of "using and abusing" local police by drafting in helicopters, sniffer dogs and the local constabulary to search scrub land and interview four suspects.

Former home secretary of Portugal Riu Pereira claimed British investigators are treating local police as "outsource workers," and would not do the same were the roles to be reversed.

Pereira's outspoken attack on British police in a Portuguese newspaper chimes with popular sentiment in Portugal, which recently saw the authorities in the Algarve threaten to withdraw their help because of negative media coverage.

Writing about the latest efforts, Pereira said: "The Portuguese authorities, especially the Policia Judiciaria, have been used and abused in the ambit of international judicial cooperation, to carry out work ordered by their British counterparts.

"From chartered Air Force helicopter flights, to search from above for holes opened seven years ago, to the return of the famous sniffer dogs, as well as quizzes of 'suspects and witnesses', everything has been done to satisfy the aims of our oldest allies. Is such deference justified?" he said.

Four suspects – known locally as 'aguidos' - were this week interviewed by Portuguese police with British officers sitting in.

"The first question that occurs to me is simple. Would the British police do the same in identical circumstances?" asked Pereira. "Of course not."

He said Portuguese police were capable of conducting their own inquiry.

"This, therefore, is the the absurdity of the situation in all its splendour. In Portugal there's a criminal investigation with the same objective, but our authorities are working, as exclusive outsource workers, for another country's ongoing investigation.

"Could it be that the reopening of the case in Portugal was simply designed to facilitate the cooperation of Portuguese police at the service of British police?

"If that is true, then there was 'manipulation' of the case. We can conclude, without making conjectures, that it reveals a good helping of subservience which prejudices our national sovereignty as a penal state."