Taiwan is in the final days of a battle over the future of equality in the country, with conservatives campaigning fiercely against LGBT advocates over a referendum on same-sex marriage on Saturday.

When Taiwan’s highest court ruled last year that same-sex marriage should be legal, supporters rejoiced after waging a years-long battle for equality. But after conservative groups rallied against the change, the government announced a referendum on the issue in August.

As voting day nears, conservative groups have deployed a reported budget of 100m Taiwan dollars (£2.5m) in an effort to push the definition of marriage as between a man and a woman only. The group Alliance for Next Generation’s Happiness, which gathered enough signatures to trigger the referendum, voiced fears for society, with spokesman Tseng Hsien-ying saying: “The collapse of the family system will deal a huge blow to society.”

Advertisements have blanketed Taiwan’s airwaves and newspapers. Misinformation has spread on social media, with same-sex marriage opponents claiming marriage equality would affect the island’s falling birthrate and make it a haven for foreigners with HIV who seek to use the national health system.

On the other side, a range of celebrities and 27 major corporations, including Google, Microsoft and IBM, have supported calls for same-sex marriage. About 100,000 people attended a rally in support of marriage equality a week before the vote in Taipei, according to local media. But polling suggests equality advocates may have a tough time at the polls. About 77% support defining marriage as between one man and one woman, according to the Taiwan Public Opinion Foundation.

Taiwan had been set to become the first country in Asia to legalise same-sex marriage when the island’s highest court said in May 2017 that barring gay couples from marrying violated “the people’s freedom of marriage” and “the people’s right to equality”.

“Sexual orientation is an immutable characteristic that is resistant to change,” the court said in its ruling. “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 ruling required same-sex marriage to be legalised within two years. While some form of legal recognition for same-sex couples is inevitable given the court’s ruling, conservatives hope to limit it to civil partnerships rather than amending the civil code on marriage.

As part of the reforms last year to increase participation in policy making among ordinary citizens, the government made it easier to propose referendums, lowering the number of signatures required to 280,000 signatures – equivalent to 1.5% of the electorate.

The situation has lead to a confusing ballot on Saturday, with a total of five questions related to same-sex life on the island, two with language in favour and three opposed. One of the questions concerns including LGBTQ material in the national curriculum, something conservatives hope to ban. It is unclear what would happen if several of the conflicting referendums pass.

Taiwanese will also be voting on a range of other issues, from nuclear and coal power use to food imports from Japan to the name used in Olympic competition, which could potentially see Taiwan barred from the 2020 Games in Tokyo.