The court ruled on Wednesday that a civil law defining marriage as a union between a man and a woman violates constitutional guarantees of equal protection.

The Taiwan News reported the court ruled that parliament has two years to either amend the law or create a new law.

Secretary General of the Judicial Yuan Lu Tai-lang said that because civil code states: "An agreement to marry shall be made by the male and the female parties" this excludes couples that are of the same sex and is therefore unconstitutional.

The landmark case was brought by gay rights activist Chi Chia-wei after the Taipei city government rejected his application to marry his long term partner in 2013.

Taiwanese President Tsai Ing-wen promised to support the right for marriage equality after winning office last year.

A tragic incident in which a French professor who had been unable to marry his Taiwanese partner of 35 years committed suicide appeared to have propelled a push for legal change.

Taiwan's The China Post reported that a draft bill by Ms Tsai's ruling Democratic Progressive Party was proposed in December to replace the words "male and female parties" in the Civil Code's marriage chapter with "two parties".

The ruling said that if the law is not changed within two years, two persons of the same sex shall be allowed to have their marriage registration "effectuated at the authorities in charge of household registration".

The ruling cited the three-decade long campaign by Chi to to marry his life partner.

The judges acknowledged it was a controversial social and political issue, but said "these petitions involve the protection of people's fundamental rights".

"Creation of a permanent union of intimate and exclusive nature for the committed purpose of managing a life together by two persons of the same sex will not affect the application of the Marriage Chapter to the union of two persons of the opposite sex.

"Nor will it alter the social order established upon the existing opposite-sex marriage.

"Furthermore, the freedom of marriage for two persons of the same sex, once legally recognised, will constitute the collective basis, together with opposite-sex marriage, for a stable society.

"The need, capability, willingness and longing, in both physical and psychological senses, for creating such permanent unions of intimate and exclusive nature are equally essential to homosexuals and heterosexuals, given the importance of the freedom of marriage to the sound development of personality and safeguarding of human dignity."

The ruling said both types of union should be protected by the constitution.

Ms Tsai wrote on Facebook: "The result of the constitutional ruling is not a victory or a defeat, no matter what attitude one holds on the same-sex marriage issue, this is the time when we look at all people around us as our own brothers and sisters."

Alex Greenwich co-chair of Australian Marriage Equality and NSW MP said: "Taiwan is joining the growing list of nations that have embraced fairness and equality for all their citizens ands it's time our parliament did too."

Amnesty International East Asia campaigns director Lisa Tassi said: "This is a huge step forward for LGBTI rights in Taiwan and will resonate across Asia."

She called on Taiwan's politicians to act swiftly.

Taiwan becomes the 23rd country to legalise marriage equality. It joins the United States, Colombia, Ireland and Finland which did so in the past two years.