"In order to show that there is nothing to fear in using other languages and to emphasise brotherhood of languages during the International Day of Mother Tongues, let me continue my speech in Kurdish," he said, just before going off air.
"Kurds have long been oppressed because they did not know any other language,'' he said. "I promised myself that I would speak in my mother tongue at an official meeting one day."
Turk received a standing ovation from about 20 members of his party, but other groups have criticised his speech, saying it was a political manoeuvre ahead of the March 29 municipal elections.
Nihat Ergun, deputy chairman of the ruling AK Party's parliament group, said the speech was a "provocation".
Koksal Toptan, head of the national assembly, found fault with Turk for speaking in Kurdish, but said that he would not be fined for defying the law.
"The official language is Turkish,'' he said. "This meeting should have been conducted in Turkish."
Under the country's law, only Turkish can be spoken in political addresses.
However Recep Tayyip Erdogan, the Turkish prime minister, spoke a few words of Kurdish at a campaign rally on Saturday.