The number of dual nationality holders who opted for Japanese citizenship exclusively and registered it with the government in fiscal 2016 topped 3,000 for the first time ever, according to the Justice Ministry.

The figure rose by more than 500 from the previous year to 3,368, the fastest increase in the past five years, with public awareness over the issue raised after lawmakers holding dual nationality made headlines.

While there is no penalty for violations, the Nationality Act requires people with multiple nationalities that include Japanese to select one and relinquish the others.

Those who acquired multiple nationalities before they turned 20 years old must choose one by age 22, while those who obtained them at 20 or older have to select one within two years.

In 2016, Renho, who was head of the Democratic Party, came under fire for retaining her Taiwanese nationality.

In another instance, Kimi Onoda, an Upper House lawmaker with Prime Minister Shinzo Abe’s Liberal Democratic Party, also admitted that year to retaining U.S. citizenship.

“Such debate might have led to increased public recognition for the scheme,” a ministry official said.

Following the partisan furor, the Justice Ministry posted a notice on its website to publicize procedures for dual nationality holders to select Japanese citizenship.

To choose to remain a Japanese national, the law stipulates that a person has to make efforts to give up foreign citizenship, or submit a report on having lost foreign nationality.

The number of dual nationality holders who chose Japanese citizenship and registered it with the government stood at 1,570 in fiscal 2006 and has since been on the rise.

Those who reported the forfeiture of foreign citizenship rose from 21 in fiscal 2006 to 150 in fiscal 2016, according to the ministry.