The Scottish Law Commission (SLC) wants to grant more marriage-like rights to cohabiting couples by changing the law on inheritance.
The SLC says cohabitants should inherit part of what they would have received automatically if they had been married to their deceased partner.
The changes would also apply in the case of adultery, so that if a married man died while living with a woman other than his wife, his estate would be split between the two women with up to half going to his mistress.
The suggestions are likely to prompt concerns among family campaigners, who argue that giving legal recognition to ambiguous cohabiting relationships will discourage people from marrying.
One in four children living with cohabiting parents will see their parents split up before their fifth birthday, compared with one in ten children of married couples.
Cohabiting couples are twice as likely to break up as those who commit to marriage.
Scotland already grants rights to cohabiting couples which have not been introduced in the rest of the UK.
Last year a woman was awarded £14,460 from her former partner after their relationship broke down.
Plans to introduce similar laws in England and Wales were put on hold last year while the operation of the Scottish system is evaluated. A spokesman for think-tank Civitas commented: “There is no need and no public demand for a cohabitation law. We have a perfectly good one already, called marriage.”
The SLC exists to promote law reform in Scotland. Its recommendations will now be considered by Justice Secretary Kenny MacAskill.