WARSAW, Poland — Jaroslaw Kaczynski, the head of Poland’s conservative ruling party, was reprimanded Wednesday by a parliamentary ethics committee for an emotional outburst in parliament last year in which he accused political rivals of murdering his brother, a former president who died in a plane crash.

Kaczynski, a lawmaker and leader of the ruling Law and Justice party, said the reprimand was expected because opposition lawmakers have a majority on the ethics committee. He called it part of a “brutal attack by the opposition,” according to the PAP news agency.

Kaczynski has long suggested that the centrist Civic Platform party, once led by current European Union president Donald Tusk, played a role in the 2010 plane crash in Russia that killed his twin brother, President Lech Kaczynski, and 95 other Poles. He has cast doubts on a Polish investigation that determined the crash was an accident.

Last July, amid a heated debate on his party’s controversial overhaul of the judicial system, a Civic Platform lawmaker drew Kaczynski’s wrath for implying that Lech Kaczynski, known as the milder mannered of the two, had held his brother back from eroding the justice system.

“Don’t wipe your treacherous mugs with the name of my late brother,” said Kaczynski, pointing angrily at his rival lawmakers. “You destroyed him, you murdered him, you are scoundrels.”