The eventual passage of the Marriage (Same Sex Couples) Bill, could lead to cohabiting relatives, or carers, being given the same legal status as married couples, the House of Lords has heard.

Baroness Deech spoke during this evening’s House of Lords debate, for its committee stage, to say that the European Court of Human Rights would be likely to support a challenge to civil partnership laws, if they were not opened up to pairs living in non-sexual relationships.

She also introduced an amendment which would have done just that, and would have included carers and relatives, and would protect people living together for decades from having to pay inheritance tax.

The chair of the Bar Standards Board, went on to say that once the equal marriage bill was passed, it would be unfair to people such as a pair of elderly sisters living together, as married couples would be treated “far better”, legally speaking.

“The situation is now even more pertinent and pressing, because the unfairness has increased,” she said.

“Civil partners and married couples, gay or straight, will be treated in law far better than, for example, two elderly sisters who share a house or an elderly father and the daughter who cares for him.”

Baroness Deech’s amendment was withdrawn during committee stage, but she warned of a challenge from the European Court of Human Rights, and said she would revisit the idea at the bill’s third reading.

She predicted that, taking into account same-sex couples being allowed to marry, “my bet is that a discrimination case before the European Court of Human Rights would probably succeed because the Convention prohibits discrimination by birth.”

In a sentiment which was challenged by other peers, she went on to say: “The state should not prefer sexual relationships, which may be short-lived and serial, over blood relationships that have proved to have endured decades.”

She continued: “I cannot resist quoting from Irving Berlin’s ‘White Christmas’- some of your Lordships may remember it: ‘Sisters, sisters, There were never such devoted sisters’.”

Baroness Knight, who recently caused controversy with comments such as that gays are “wonderful,” and “really good at antiques”, chimed in to say: “As the years go by the injustices mount. There will be many people who would have been helped if the original amendment had gone through.

“I for one am not prepared to sit here and be told for years and years and years ‘tomorrow, tomorrow, tomorrow’ for tomorrow never comes.”

Lord Alli was heavily critical of the amendment, however, saying it would “devalue” civil partnerships.

Baroness Deech’s amendment was also supported by Baroness Butler-Sloss, who said earlier this year that the Government should stop “faffing around with gay marriage”, and the Bishop of Ripon.