An independent research organisation has denied a claim by Conservative peer Baroness O’Cathain, that one of its studies finds that children “do best” when raised by straight, married parents. She incorrectly cited it in her arguments against equal marriage.

PinkNews can reveal that the Institute for Fiscal Studies has denied the claims by the Tory peer, noting that the study does not examine the differences, if any, between outcomes of straight and gay parents.

Speaking in the House of Lords yesterday, Baroness Detta O’Cathain told peers that marriage should be reserved for heterosexual couples, claiming that children show “superior social, emotional and cognitive development” when raised by a married man and woman.

“The evidence from social science is now emphatic that children do best when raised by their married mother and father. I mention just one example: a paper from the Institute for Fiscal Studies observes that, even by the age of three, there are ‘significant differences’ in outcomes between children born to married parents and those born outside marriage. Children born to married parents showed superior social, emotional and cognitive development. There are many other studies which provide powerful evidence of the positive benefits of marriage. Should we throw this up in the air?” she said.

A spokeswoman for the IFS, in an email to a PinkNews reader, said the study did not hold up Baroness O’Cathain’s claims, and that it did not look at the gender of the parents featured in the research.

“Our report does NOT claim that child outcomes are better for children born to a married mother and father as opposed to married couples of the same sex,” she said. “There were insufficient numbers of same sex couples in the data we used to allow us to conclude anything about this.”

She also denied that the report referred to by Baroness O’Cathain examined in any way the gender of the parents, and whether it could make a difference to child outcomes.

“Our report certainly does not support Baroness O’Cathain’s claim that ‘The evidence from social science is now emphatic that children do best when raised by their married mother and father’ as opposed to two married mothers or two married fathers. In fact, we find that any apparent benefit of marriage is in fact accounted for by the characteristics of couples that choose to get married (for example more highly educated couples).”

The Conservative peer, known for opposing civil partnerships and adoption rights for gay couples, had also suggested it had been “wishful thinking” to believe the same-sex marriage bill had been dropped when it was not mentioned in the Queen’s speech.

She ended by urging the government “to admit graciously that this has been a great mistake and drop the Bill.”