(CNN) The European Parliament has launched a hate speech investigation into a Polish politician after he stated that "women must earn less than men, because they are weaker, they are smaller, they are less intelligent" during a debate this week on the gender pay gap.

Janusz Korwin-Mikke is an independent member of the European Parliament who founded a right-wing political party, the Coalition for the Renewal of the Republic -- Freedom and Hope, in 2015. He has previously said that women should not be allowed to vote and was investigated for incitement to rape in 2014 over remarks he made to the European Parliament.

Outraged by his comments Wednesday, another parliamentary member, Iratxe Garcia Perez of the Spanish Socialist Workers' Party, launched a forceful counterattack.

"I know it hurts and worries you that today women can sit in this house and represent European citizens with the same rights as you," she said. "I am here to defend all European women from men like you."

The president of the Socialists and Democrats Group also responded, urging European Parliament President Antonio Tajani on Twitter to "sanction Mr. Korwin-Mikke for his shameful statements."

According to a European Parliament statement published Thursday, Tajani has launched an investigation on the basis of Rule 11 of Parliament's Rules of Procedure.

This rule states that "members' conduct shall be (characterized) by mutual respect" and "members shall not resort to defamatory, racist or xenophobic language or (behavior) in parliamentary debates."

"Penalties range from a reprimand to a fine and temporary suspension," according to the statement.

CNN has tried unsuccessfully to contact Korwin-Mikke for comment about the investigation.