The annual Pink Dot gathering will be held on Saturday at a downtown park -- the only place where demonstrations are permitted -- with organisers aiming to top last year's record turnout of more than 20,000 people.

The carnival-like rally draws a diverse array of straight and gay participants decked out in bright pink attire including hats and even facial hair dyed in the colour organisers picked to represent the freedom to love.

The term "Pink Dot" is a play on Singapore's nickname -- "The Little Red Dot" on the world map.

Pink Dot has been held annually since 2009 and enjoys the support of local celebrities as well as internet giant Google and financial firms Barclays and J.P. Morgan, in a show of support for diversity in society and the workplace.

But this year, Muslim and Christian conservatives in the multi-ethnic island are fighting back.

Lawrence Khong, a senior pastor with the 10,000-strong Faith Community Baptist Church, has led the charge to ban the event, saying it is an affront to morality and "family values" in the nation of 5.4 million people.

Khong is a longstanding opponent of a campaign to repeal Section 377A, a provision in the Singapore penal code that makes sex between men a crime.

The provision dates back to British colonial rule and carries a maximum penalty of two years, but it is not actively enforced by the Singapore government.

"We must let our government know that, in allowing the Pink Dot Event to continue without restraint, they are more than tolerating the gay agenda," Khong wrote in a Facebook post.

"They are bordering on endorsing and emboldening the LGBT claim to gay rights," he wrote, using the acronym for the Lesbian, Gay, Bisexual and Transgender community.

The pastor, who leads a network of Protestant churches called LoveSingapore, professed support for a peaceful protest led by Ustaz Noor Deros, a Singaporean Muslim teacher.

- Muslims plan 'white' counter-protest -

Noor last week launched a "WearWhite" campaign urging Muslims to shun Pink Dot and instead wear white garments to mosques on the same night as the rally, which coincides with the eve of the Muslim holy month of Ramadan.

"The movement's genesis was from our observations of the growing normalisation of LGBT in Singapore," WearWhite's website said. Its Facebook page has attracted over 3,700 'likes'.

Archbishop William Goh, in a letter to local Roman Catholics, also said "the LGBT movement is gaining momentum" and reiterated the church's stand that gay sexual relationships "are not in accordance with the plan of God."

But he also spoke out against "discrimination of any kind".

An umbrella group of Protestant churches affirmed its belief that homosexual and bisexual practices are "contrary to the teaching of the Bible" but called for "grace and restraint" by the Christian community in dealing with the rally.

Organisers of Pink Dot said they were "saddened that certain quarters have reacted negatively to our efforts at creating a more loving and embracing society."

And Singapore's leading activist groups issued a statement condemning rising anti-gay rhetoric from religious conservatives.

"A worrying trend has emerged on social media with voices calling for gays and lesbians to be targeted for public shaming and harassment," said the statement signed by nine groups including Maruah, Singapore's main human rights organisation.

The Pink Dot event usually passes without much controversy. Saturday's gathering, which will include speeches and musical performances, will culminate with the crowd forming a giant pink dot after dusk by holding LED lights.

Siew Kum Hong, a former lawmaker who has championed LGBT rights, said the pushback this year stemmed from "a clear and deliberate escalation by the Christian right".

Siew launched a landmark parliamentary petition to repeal Section 377A in 2007. It was unsuccessful but helped galvanise the gay-rights movement.

"The current position is simply not tenable, and the pressure to repeal will only continue to grow," he said.

Officials have urged Singaporeans to practise restraint in debating LGBT rights.

"We just have to be a society where you don't go pushing your own beliefs and preferences, but at the same time everyone keeps the balance in society and avoids creating conflict," Deputy Prime Minister Tharman Shanmugaratnam said.

Even though it is not enforced, the government says Section 377A has to stay on the books because most Singaporeans are conservative and do not accept homosexuality.

A survey of 4,000 citizens by the government-linked Institute of Policy Studies earlier this year found that 78.2 percent of the local population felt same-sex sexual relations were wrong.