The court said that the investigating judge, Jean-Marc Connerotte, could no longer be impartial because he had attended a fund-raising dinner last month for the families of missing children.
Outside the Justice Palace, hundreds of protesters jeered the Supreme Court and shouted "Murderers!" At a Volkswagen car factory on the outskirts of Brussels, hundreds of workers staged a spontaneous strike.
Some 300,000 people had petitioned the court to retain Mr Connerotte. His leading role in the case had restored some credibility to a justice system criticized for bungling the investigation of Marc Dutroux, a convicted child rapist.
Mr Connerotte became a national hero last August after his investigators rescued two children from a dungeon on Dutroux's property, found the bodies of four kidnapped young girls and uncovered a child-pornography network.
In Belgium, an investigating judge collects evidence in criminal cases and prepares it for trial. But the Supreme Court ruled yesterday that Mr Connerotte's attendance at the fund-raising dinner on 21 September meant that he could no longer be impartial.
"The impartiality of a judge is a fundamental rule of the judicial order," the five-member panel wrote.
The charges were brought by Dutroux's attorney, Julien Pierre, who said the Supreme Court had acted with "infinite wisdom" in dismissing Mr Connerotte.
The parents of the murdered girls and the prime minister had pleaded with the judges to keep Mr Connerotte in charge of the investigation. "I have lost all faith in justice," said Paul Marchal, whose daughter was found buried on Dutroux's property. "What's the use of a team if you no longer have a leader?" he said. "If you don't need it, why have a king? Why have a prime minister?"
In the Eighties, Dutroux was imprisoned for sexually abusing five children, but he was released in 1992 after serving only about half of his 13-year sentence after convincing social workers and psychiatrists that he was rehabilitated.
Children soon started disappearing across Belgium, but police failed to conduct a concerted investigation. At least a half-dozen children and young girls remain missing. Numerous tips pointed to Dutroux, including one from his mother. But police failed to take action or refused to share information.
Errors piled up even as they closed in on Dutroux. Police searched his house twice, but failed to find the hidden girls. But under Mr Connerotte's direction, two young girls were found in a secret chamber in the basement of his home in Charleroi, 37 miles (60 km) south of Brussels. The bodies of two others whom he said had starved to death in the cellar were dug up on another of his properties. He admitted kidnapping two more girls who disappeared a year ago.
Mr Connerotte's aggressive tactics had managed to restore a small measure of public confidence. He was responsible for jailing a dozen people, and Belgian media reported last weekend that he had found evidence of at least one other paedophile network.
The rest of Mr Connerotte's team will stay on, including a close ally, Michel Bourlet. The investigating judge will most likely be replaced by Jacques Langlois, a district substitute who has been on the job for a month.
Mr Connerotte lives 120 miles (195 km) south-east of Brussels and did not attend the court hearing. He had said in advance that he would not comment on the decision.Reuse content