BRUSSELS (Reuters) - The Belgian king’s younger brother faces a dressing down from the prime minister after demanding that politicians and the royal family “stop bugging” him over claims his business ventures are losing money.

The summons from Prime Minister Charles Michel, amid some concern for the stability of the monarchy, came on Thursday after Prince Laurent, a sports car-loving 53-year-old, let off steam at a journalist who quizzed him over the financial health of his renewable energy interests.

“This is really starting to piss me off,” he said in remarks in French captured by a television camera. “If certain politicians would get off my back, if my family would get off my back, I could show you that these accounts are positive.”

Michel told the Belgian parliament, where often squabbling ranks of French- and Dutch-speakers look to the royal house and King Philippe to hold the country together, that the family’s enfant terrible had, not for the first time, gone too far.

Calling his language “totally inappropriate”, the premier said: “As a member of the royal family, the law says he must be reserved in his public statements.” Michel, who has yet to fix an appointment, would “remind him of the rules” and insist he show respect to the people’s elected representatives.

Last week, Michel reprimanded Laurent for meeting the prime minister of Sri Lanka without clearing it with the government. The prince has also been rebuked over expense claims and some parliamentarians want a cut in his 300,000 euro ($320,000) annual allowance.

Philippe, who took the throne in 2013 when their father Albert abdicated, has caused few waves. But the behavior of his former naval helicopter pilot brother has raised fears for the future of the monarchy.

“Laurent is slowly killing the royal house,” a Belgian official said, arguing the government must rein him in.

Royal correspondent Pierre De Vuyst told broadcaster RTL that Laurent was “going off the rails” by attacking politicians and his own brother: “That doesn’t seem very smart given a lot of people are against the royal family right now,” he said.

Philippe, 56, is the seventh King of the Belgians since the German prince Leopold of Saxe-Coburg, uncle of Britain’s Queen Victoria, was installed in 1831 after independence from The Netherlands. Laurent, 12th in line today, has three children with his half-English wife Princess Claire.