In a public whipping delivered before parliament, Leterme said the 47-year-old prince "ignored his obligations by maintaining his trip despite formal advice from the government and the palace."

Prince Laurent’s trip to Kinshasa this month on an animal welfare mission has provoked a furore in Belgium, with MPs calling for his state allowance to be cut and the premier warning he has "rights" but also "duties."

The youngest son of King Albert II and Queen Paola, and 12th in line to the throne, heads an association defending the rights of domestic and wild animals, the Prince Laurent Foundation.

But five decades after Congo won its independence from Belgium, official visits, even when private, remain diplomatically delicate with the government keen to avoid seen favouring any single political party as the country heads for presidential elections in November.

"By accepting privileges and facilities linked to his status from his hosts, and having had contacts with political leaders, even if informally, Prince Laurent … made an error of judgment," Leterme said.

President Joseph Kabila, who was elected in 2006 and is expected to run again, greeted the prince during his March 15-22 trip, the premier said.

Leterme, who told parliament he had telephoned him on the eve of his departure to ask him to postpone the trip, said the prince’s status "imposes obligations and duties, in the same way it confers rights".

"The prince must be conscious of the required balance he must respect between his rights and duties. I don’t doubt he will heed my remarks and clearly choose between the strict respect of this balance, or the definitive renunciation of his rights."

Recently stripped of his driving licence for two weeks for speeding, and castigated for travelling business class with economy-class tickets, the prince has a 210,000-euro yearly allowance.

Speaking on radio, he said "it was a private research trip, with a purely scientific aim, and not at all political."

"It was paid for by the Foundation and not by Belgium."