Tomorrow, the Civil Partnerships, Marriages and Deaths Bill – which would allow opposite sex couples to enter into civil partnerships – gets its second reading in the Lords. The bill has already made it through the Commons; and if the formidable Equal Civil Partnerships lobby group succeeds, it will become law by the end of the year. Supporters of the bill say it is a minor and sensible tweak to messy marriage legislation. They make the argument that a system allowing gay couples to choose a civil partnership over marriage, if it suits their purposes, but doesn’t afford the same privilege to straight couples is quirky and unfair. The legislation provides Parliament with a harmless way of fixing this. But the bill's supporters are ignoring the reality: allowing straight people to have civil partnerships is a big mistake.