The Scottish Government has introduced a Bill to allow heterosexual couples to enter into a civil partnership rather than a marriage.
The move follows last year’s Supreme Court ruling that offering civil partnerships only to homosexual couples is discriminatory.
Westminster politicians already plan to legalise heterosexual civil partnerships in England and Wales by the end of 2019.
After a public consultation, the Scottish Government chose to extend civil partnerships to heterosexual couples rather than scrap them.
The Christian Institute’s Ciarán Kelly said: “Marriage – with its public promises of lifelong faithfulness – is the gold standard of commitment. It is beneficial for the individuals involved and for society as a whole.
“Holyrood politicians are giving their backing to ‘marriage lite’ – all the benefits of marriage but without the responsibilities.
“Time would have been better spent resolving the genuine injustice suffered by huge numbers of other house-sharers who are excluded from civil partnerships and can get hit with an enormous inheritance tax bill.
“A daughter living with her elderly mother, a grandson living with his infirm grandfather, a friend who looks after a disabled person on a long-term basis – these are the injustices that ought to be addressed.”