Lord Maginnis spoke out in strong opposition of allowing same-sex couples to marry in church, repeatedly referring to it as "unnatural and deviant behaviour" which shouldn't be "imposed" on society.
The senior politician then went further, telling the Stephen Nolan Show that gay relationships were "a rung on the ladder" towards bestiality.
Referring to campaigns to allow the same rights for same-sex couples when it comes to marriage, Lord Maginnis said it all came down to sexual practice.
"Does that mean that every deviant practice has to be accommodated? Will the next thing be that we legislate for some sort of bestiality?" he asked.
Lord Maginnis was speaking in a personal capacity without our knowledge or permission and his comments do not reflect Ulster Unionist Party policy.
John O'Doherty from The Rainbow Project, a group representing the gay community in Northern Ireland, said the comments were "completely disgusting" and only served to fuel serious negative attitudes which already exist.
"When we hear such rampant homophobia coming from a senior politician here in Northern Ireland, where else would we expect people's attitudes to come from?" he said.
"At a time when an Equality Commission survey has found that negative attitudes towards lesbian, gay, bisexual and transgender people in Northern Ireland have significantly hardened, it is reprehensible that a senior politician should claim that people in loving and committed relationships are 'unnatural' and 'deviant'."
Calling on Lord Maginnis to retract his comments, Mr O'Doherty added: "Many LGB&T people feel isolated and vulnerable in their communities and the ridiculous claims made by Lord Maginnis only compound this isolation.
"What was equally worrying was that Lord Maginnis advised that young people coming to terms with their sexual orientation should seek the assistance of a physician or psychiatrist as if there is something wrong with them.
"This is completely unacceptable."
During Wednesday morning's radio show, Lord Maginnis moved to defend his argument when challenged.
"You've asked me to define it as I see it, as it affects my church, as it may affect children ... I just do not believe that we should be doing anything to encourage this deviant practice," he said.
"If my next-door neighbour is homosexual, I will treat him with the same day-to-day respect as I will treat the neighbour on the other side."
Any young people listening this morning should know that there is nothing wrong with them, and that help and support is available for them at The Rainbow Project.
A survey by the Equality Commission has been looking into how attitudes towards people from different backgrounds have changed in Northern Ireland over the last six years.
The findings, published on Wednesday, show increased negativity - including towards the gay community.
Just over a quarter of people surveyed said they would object to having a gay neighbour.
While the UUP distanced itself from the remarks by Lord Maginnis, a call has been made for party leader Mike Nesbitt to take disciplinary action over the issue.
Alliance Party chief whip Stewart Dickson said he was appalled by the "outrageous" remarks.
"There is no way that Mike Nesbitt can get away with saying that Lord Maginnis was speaking in a personal capacity," he said.
"He was representing the UUP when he spoke and I am sure that many people will take his words as UUP policy until strong disciplinary action is taken."
The SDLP's spokesman on equality issues, Colum Eastwood, said both the survey's findings and the comments by Lord Maginnis brought into question "the illusion of progress".
He added: "The attitudes contained within this survey, so frighteningly personified by Ken Maginnis's startlingly offensive expressions of archaic ignorance, are a timely reminder that a resilient residue of prejudice remains in our society.