Two Osaka subway drivers have sued the city's municipal government after their bonuses were cut because they refused to shave off their beards.

"Growing a beard is part of individual freedom, just like choosing clothes or hairstyles," said a lawsuit filed Wednesday with the Osaka District Court.

"The city's grooming standards violate this freedom guaranteed under the Constitution."

Both men are in their 50s and are employees of the Osaka Municipal Transportation Bureau. They are seeking ¥2.2 million each in damages for mental suffering, along with payment of the missed bonus component.

The two men had beards for more than 10 years when the transportation bureau in 2012 introduced grooming standards that banned them. The policy was prompted by then Mayor Toru Hashimoto.

Because the drivers refused to comply, they received lower personnel evaluation ratings that reduced their bonus payments, the lawsuit said.

"I have never neglected to groom my beard and never received complaints from passengers about my beard," one plaintiff told a news conference. "I just can't accept to be told I am badly groomed just because I grow a beard."

The Osaka Bar Association has urged the transportation bureau to scrap the no-beard rule, calling it a violation of human rights.

Commenting on the lawsuit, Hirofumi Yoshimura, the current mayor of Osaka, said the standards were "for letting passengers use the subway pleasantly" and were "not excessive."