What is more strange, however, is the contortions they must perform for this to be achieved.

There is nothing wrong with ideas that encourage those who are in love to tie the knot, but it cannot be at the expense of those couples who live under the same roof but decide they don't want a gold band around their finger.

Conservative plans to deny co-habiting couples the same rights as those who marry raise more questions than they answer, such as, what can a government to do change social patterns?

The number of people getting married has declined steadily for more than 30 years. This seems to have passed by Iain Duncan Smith when his Centre for Social Justice proposed state backing for classes to prepare couples before their wedding.

The definition of a family has changed remarkably in the last three decades, leaving David Cameron caught between shoring up his core support of older, more traditionalist voters and appealing to the millions of young people who choose not to marry. Afraid of alienating either group, he has so far talked around the issues with glib assertions that Britain is "broken".

Mr Duncan Smith may be right when he says that married couples are more likely to stay together than those co-habiting, but attempts to discourage "informal" relationships are wrong. He may be left standing at the altar on this one.