The head of the Roman Catholic Church in Scotland Cardinal Keith O’Brien has defended comments at the weekend in which he described equal marriage rights as ‘grotesque’ and the legalisation of gay marriages as being akin to the legalisation of slavery and warned of ‘further aberrations’.

Defending the comments he made at the weekend likening equal marriage to slavery and saying it was a violation of human rights, he told the Today programme on Radio 4 this morning it was “time to call a halt now to what you may call progress in society”.

“Further aberrations” would ensue and “society would be degenerating even further than it has already degenerated into immorality” if the government were to allow gays to marry, he said.

He added that he was not “saying it is grotesque, but perhaps to some people it might appear grotesque” and it would “shame” the UK.

While Scotland will not be included in Westminster plans for gay marriage, the consultation on which is due to begin soon, the Scottish government has said it is “minded” to introduce marriage equality and completed its own consultation last year.

A Home Office spokesman said the British government believed that “if a couple love each other” and want to commit to a life together, they should “have the option of a civil marriage, irrespective of their sexual orientation”.

Cardinal O’Brien wrote at the weekend: “All children deserve to begin life with a mother and father; the evidence in favour of the stability and well-being which this provides is overwhelming and unequivocal.”

The cardinal was repeating a comment about child welfare he had made in December at the launch of a coalition against equal marriage in Scotland which his press office was unable to substantiate.

Alleging gays to have “exceptionally medically hazardous” relationships, it relied on a study performed at the height of the AIDS epidemic on gay men in a Canadian city whose own authors said in 2001 would have no wider, modern application.

Authors wrote that it “appears that our research is being used by select groups in US and Finland to suggest that gay and bisexual men live an unhealthy lifestyle that is destructive to themselves and to others.

“These homophobic groups appear more interested in restricting the human rights of gay and bisexuals rather than promoting their health and well being.

“The aim of our research was never to spread more homophobia, but to demonstrate to an international audience how the life expectancy of gay and bisexual men can be estimated from limited vital statistics data.”

Cardinal O’Brien continued: “I am not saying it is grotesque, but perhaps to some people it might appear grotesque.”

He added: “I think if the UK does go for same sex marriage it is indeed shaming our country.

“We’re taking standards which are not just our own but standards from the Declaration of Human Rights of the United Nations where marriage is defined as a relationship between man and woman and turning that on its head [...] I would say that countries where this is legal are indeed violating human rights.”

Conservative MP Daniel Byles tweeted that Cardinal O’Brien had been “bizarre and incoherent” in his arguments on the BBC this morning.

Stephen Gilbert MP said: “God made all men and women equal – O’Brien decided some are more equal than others.”

Of the cardinal’s comments at the weekend, George Broadhead of the gay humanist charity the Pink Triangle Trust, said: “Has the cardinal not heard that gay marriage has already been legalised in no fewer than ten countries: Argentina, Belgium, Canada, Iceland, Norway, Portugal, South Africa, Spain, Sweden and The Netherlands? I am not aware that any of these countries have suffered shame or any sort of pariah status as a result. This just shows how out of touch with reality the Roman Catholic Church has become.”

Ben Summerskill, Chief Executive of Stonewall wrote: “When you read the insulting tone to which Cardinal O’Brien descends on marriage, you sense an argument already lost.”

Peter Tatchell, who coordinates the Equal Love campaign, said of the cardinals’ comments at the weekend: “If he supports marriage, the Cardinal should welcome the fact that many lesbian and gay couples want to get married. Same-sex marriage does not detract in any way from heterosexual marriage. It does not diminish or devalue marriages between opposite-sex couples.

“Allowing same-sex marriage does not undermine marriage; it strengthens it.

“Cardinal O’Brien has attacked government plans as an attempt to redefine marriage. But the churches have redefined marriage in the past. They no longer oppose divorce and the remarriage of divorced couples. There is no reason why marriage should not be redefined to include lesbian and gay couples.

“Gay marriage is about love and commitment. These are Christian values, so I don’t understand why the Cardinal objects to gay couples getting married.”