Let's be clear - this policy is not about supporting children: only 35% of the families who would gain from the policy have children, and only 17% have children under 5. And of course, it wouldn't help the 1 in 4 kids who grow up in a single parent household. Nor is about helping the poorest: workless families and families where both parents are working to make ends meet would all miss out.

No, this policy is specifically about "sending a message" about how we should live our lives: that marriage is best. A tax break to promote this 1950s family model has been met with outrage and incredulity. Government has absolutely no right to judge our families! We agree with Nick Clegg when he has repeatedly criticised the idea, saying it is a "throwback to the Edwardian era" and adding: "Miriam and I got married for love, not for three quid a week. It's patronising drivel."

The Coalition Agreement stipulates that Liberal Democrat MPs can abstain on the vote to introduce the measure. But Don't Judge My Family, the grassroots campaign against the marriage tax allowance, knows that introducing a tax break to incentivise one kind of family model over others is completely counter to what Liberal Democrats believe in, as Caron Lindsay argued here earlier this week. We'll be urging Lib Dems to vote against it, and hope you'll help us.

David Cameron wants to "send a signal" that marriage is better than any other type of relationship. Sign up here to send a signal back: don't judge my family!

* Julianne Marriott is Campaign Director of Don't Judge My Family.