A lawsuit against the government is being launched by five people who claim their constitutional rights are being violated

This article is more than 9 years old

This article is more than 9 years old

Five people in Japan are poised to launch an unprecedented lawsuit against the government, claiming that a civil law forcing them to choose a single surname after marriage violates their constitutional rights.

If they succeed, married men and women will for the first time be able to retain their own surnames, dealing a blow to one of the few remaining legal obstacles to gender equality.

In the vast majority of cases, women are required to relinquish their maiden name after marriage, although a small number of men take their wife's name.

Critics say the time has come to modernise the law in Japan, the only G8 nation with laws governing marital surnames.

The plaintiffs argue that the civil code's requirement that a single surname be chosen contradicts articles of the constitution guaranteeing individual liberty and equal rights to husband and wife. The five are also seeking ¥1m (£7,727) each in compensation from the government.

Kyoko Tsukamoto, who changed her maiden name in the family registry after marrying in 1960 but retained it in daily life, said the law had contributed to a "strong loss of self" and caused psychological damage.

"My husband and I still love each other, but this and the issue of Tsukamoto are different," said the 75-year-old former teacher. "I thought I would get used to my husband's name, but I couldn't. I felt a strong sense of loss growing inside me."

Opposition from conservative politicians delayed previous attempts to change the law. In 1996 the justice ministry devised an amendment that would give married women the right to retain their maiden names, but the move was blocked by MPs who said it would undermine the family unit.

The current government, led by the centre-left Democratic party, supports a change in the law but has yet to act amid opposition from a minor coalition ally.

"There were expectations that it could be enacted, but unfortunately this did not happen. They do not want to wait any longer," said the plaintiffs' lawyer, Fujiko Sakakibara.

The law has forced some couples to take drastic action. Tsukamoto and her husband divorced in 1965 so that she could regain her maiden name, but remarried when she became pregnant because civil law can impinge on the inheritance rights of children born out of wedlock.

Critics say the civil code, enacted in 1896 and amended by the US occupation forces after the second world war, ignores dramatic postwar changes to the role of women in the home and workplace.

The movement for change gathered pace in the 1980s when more women entered the workplace. Many complained that changing their names after marriage was detrimental to their career prospects and affected relationships with colleagues.

Yet the Japanese are divided over the issue: in a 2009 survey 49% said they supported a change in the law, while 48% were opposed.

Women still have to use their registered surnames on official documents such as passports and health insurance cards.

Many companies allow married women to retain their maiden names at work, but for Tsukamoto, who married in 1960, unofficial acceptance is not enough.

"Now I am 75, and I was shocked to realise that I can no longer do the things I was able to do even last year," she said. "That's when I thought, I am Kyoko Tsukamoto … and I want to die as Kyoko Tsukamoto."