Environment Minister Shinjiro Koizumi has expressed support for enabling married couples to use different family names, a major break with Japanese tradition, after a ruling party lawmaker’s heckling in the Diet brought the contentious issue back into the spotlight.

“I want to create a society in which people can live based on their own values. I’m positive about giving (couples) such an option,” Koizumi said at a news conference Friday.

“It’s quite often the case in Japan that simply offering an option sparks the kind of stiff resistance you’d expect to abolishing the existing system,” said Koizumi, widely touted as a potential future prime minister.

The issue of whether to allow married couples to legally use different surnames has gathered renewed attention since a lawmaker from the ruling Liberal Democratic Party heckled an opposition party leader promoting it earlier this week. Koizumi is also an LDP member.

“Don’t get married then!” the lawmaker — identified by opposition party lawmakers as LDP Lower House member Mio Sugita — shouted at Yuichiro Tamaki, leader of the Democratic Party for the People during a parliamentary session on Wednesday.

At the time, Tamaki was sharing the story of a young man who was told by his girlfriend that she did not want to get married because she would then need to change her surname. The Civil Code and the Family Register Law require the use of a single surname by members of the same family.

Although the Civil Code does not say which of the partners must give up their surname on marriage, it is customary for a wife to take her husband’s surname.

Major opposition parties on Friday urged Tadamori Oshima, the Lower House speaker, to find out who the lawmaker was, as Sugita has kept silent over her alleged heckling.

The LDP has many conservative lawmakers who place importance on traditional values.

Prime Minister Shinzo Abe, who also serves as LDP president, responded to Tamaki on Wednesday by saying that enabling the use of different surnames affects “the way families should be” and there are various views about it among the public.

Koizumi, one of the sons of former Prime Minister Junichiro Koizumi, made headlines with his marriage to TV personality Christel Takigawa and a recent decision to take paternity leave, a rarity in Japan, especially among politicians.