Taiwan's parliament legalised same-sex marriage on Friday in a landmark first for Asia as the government survived a last-minute attempt by conservatives to pass a watered-down version.

The island's lawmakers comfortably passed a law allowing same-sex couples to form "exclusive permanent unions" and a second clause that would let them apply for a “marriage registration” with government agencies.

The vote is a major victory for the island's LGBT community who have campaigned for years to have similar of equal marriage rights as heterosexual couples and places the island at the vanguard of Asia's burgeoning gay rights movement.

In recent months conservatives had mobilised to rid the law of any reference to marriage, instead putting forward rival bills that offered something closer to limited same-sex unions. But those bills struggled to receive enough votes.

Hundreds of gay rights supporters gathered despite heavy rain near Taipei's parliament as a mammoth legislative debate got under way over an issue that has bitterly divided the island.