An online petition in objection to the Conservatives and Democratic Unionist Party (DUP) forming a government has gathered more than 500,000 signatures.
The DUP were accused of being a "dangerous group" on the page, which strongly criticised the party's attitudes to the LGBT community.
The party's stance on abortion, the death penalty and the teaching of creationism as scientific fact was also condemned.
Protests against an alliance between the two parties have also taken place outside Downing Street for a second day running.
It comes as Scottish Conservative leader Ruth Davidson said she has received assurances from the Prime Minister over gay rights should the Tories do a deal with DUP.
Ms Davidson, who is gay, spoke out after Theresa May outlined a plan to seek a deal with the socially hardline party, which has 10 seats in the Commons, to prop up her minority administration.
The DUP's controversial views on LGBT rights
Northern Ireland is the only area of the UK where same-sex marriages are not legal.
The DUP used a controversial "petition of concern" to veto its legalisation in 2016.
The party has often found itself embroiled in controversy over its stance on gay rights issues.
Founded on the evangelical principles of the late Ian Paisley's Free Presbyterian church, Northern Ireland's largest political party has been repeatedly at odds with the region's LGBT community.
While the party insists it is protecting the "traditional" definition of marriage, critics have denounced its stance as homophobic.
Former first minister Peter Robinson's wife Iris, who was an MP at the time, once described homosexuality as an "abomination", while the MP son of Dr Paisley, Ian Paisley Jr, said he felt "repulsed" by homosexual acts.
A party councillor in Ballymena reportedly claimed Hurricane Katrina, which killed more than 1,500 people in the US, was God's revenge for New Orleans hosting an annual gay pride event.
In the 2015 general election campaign, DUP health minister Jim Wells resigned amid a controversy about remarks he made about same sex couples.
Defending her party's stance on gay marriage in a recent interview, leader Arlene Foster insisted those who characterised the DUP as anti-gay were wide of the mark.
"They are wrong and they need to understand why we take those positions from a faith point of view and why we want to protect the definition of marriage," she said.
"I could not care less what people get up to in terms of their sexuality, that's not a matter for me, when it becomes a matter for me is when people try to redefine marriage."
What are the DUP's other controversial views?
The DUP opposes abortion and after Arlene Foster was elected leader last year, she vowed to work to prevent abortion rights outlined in the Abortion Act 1967 from being extended to Northern Ireland.
Abortion is banned in the region, even in cases of rape, incest or when the foetus has no chance of survival after birth.
The party is also pro capital punishment. In 2011, it reopened calls for Westminster to debate bring back capital punishment.
The DUP counts creationists among its senior members, with former health minister Edwin Poots believing earth was created 4,000 years ago.
Thomas Buchanan, deputy chair of the learning and employment committee, has endorsed an event promoting creationism to be “taught in every school” that will “offer helpful practical advice on how to counter evolutionary teaching”.