Why don't some parents like taking advice from non-parents?
An MP has apologised after making reference to the childlessness of former Children and Families Minister Sarah Teather. But why do some people question non-parents' ability to give advice about children?
"She certainly didn't produce one of her own."
So was Sarah Teather described by fellow MP Tim Loughton who served alongside her at the Department for Education.
The remarks were widely condemned as offensive and sexist. Loughton subsequently apologised and said he had not intended to criticise the former minister personally.
However, the row revealed a little-acknowledged fact. For some people, opinions about child-rearing from those who have thus far not had any children are worth less than those who have.
About a month before Loughton's comments were made public, the website Mumsnet debated the issue of "advice from childless friends". To many, this advice was largely unwelcome.
"I mean honestly do you actually believe those 4 hours that you have cared for a child equate to the harsh reality of parenting?" wrote one poster. "Unless you are a parent you can't possibly have any concept of what parenting is like," added another.
Other board members dissented. There are, after all, plenty of teachers, midwives, carers and other childcare professionals who don't themselves have offspring, but carry out their jobs diligently and effectively.
Nonetheless, it's undeniable that many parents don't like being told what to do by people who have never changed a nappy or been kept awake by a crying baby.
Justine Roberts, Mumsnet's chief executive, acknowledges there is a body of opinion on her site that finds child-free people "fussing over" parents annoying, especially when they haven't had to engage with the tiring, unromantic side of parenthood. "It's about understanding how irritating toddlers are," she says.
But she draws a distinction between these kind of attitudes and the comments made by Loughton. It's one thing an unqualified non-parent offering words of wisdom, it's another when either a childless expert, or a politician who works with experts, is involved.
"I've never seen any criticism of Sarah Teather on Mumsnet," Roberts says." To be honest I think it's just mean. It's about characterising a woman's worth as whether she has children."
Others agree that the gender of the 39-year-old ex-minister made her a particular target.
Mainstream society holds women to very different standards when it comes to families, according to Tina Miller, professor of sociology at Oxford Brookes University, whose research focuses on depictions of parenting.
"If 39-year-old Simon Teather was a minister, his fertility would not be invoked," says Miller.
"One of the things about women and motherhood is that we are basically socialised from the moment we are born into the expectation that we will have children. If you don't you have to provide an explanation." For her part, there has been no statement on the row issued by Teather.
Likewise, it appears that family policy, her former portfolio, attracts an expectation of first-hand expertise that other Whitehall departments do not.
Defence ministers are rarely criticised for never having served in uniform, and lacking a background in finance and economics tends not to be an impediment towards becoming chancellor of the Exchequer (the last four occupants of 11 Downing Street have been graduates in modern history, law, history and law respectively).
And yet some of the best-known dispensers of family advice are themselves child-free.
Jo Frost, television's Supernanny, has no children herself, though she has worked in childcare since 1989. The controversial parenting guru Gina Ford does not have any offspring, yet her parenting books are said to account for 25% of the entire market.
Many child-free people have not chosen their child-free status, yet find fulfilment working with or caring for other people's children. Others may have decided to have children later in life, or not at all, yet be capable of displaying empathy for young people and parents alike.
Corinne Sweet built a successful career as a child psychologist before giving birth at the age of 43. For many years she had insisted she did not want a family of her own before changing her mind.
Sweet says being a parent transformed her outlook, but she was no less capable of working with children before she gave birth.
"I worked a lot with young people before I had a child," she says. "Being a parent changes your perspective but that doesn't mean to say I couldn't empathise with children beforehand.
"There are plenty of teachers, therapists, doctors, coaches, who don't have children themselves but have the training and professionalism to do their job."
At the same time, however, she acknowledges that there were aspects of what it means to be a parent - the visceral, emotional side - that she could not have understood before she became one herself.
The success of Mumsnet and similar sites rests on the fact that sharing knowledge about the nuts and bolts of parenting, and the sense of responsibility that raising offspring brings, acts as a bonding process. Because almost always non-parents can't know what it's like.
"No-one can tell you what it's like to be a parent," says Miller. "Nothing can prepare you for that.
"If you aren't a parent yourself you can have ideas yourself but you can't know."
What's more, the very fact that parenting is such a personal and emotive subject means many will naturally resent outsiders offering advice, especially if it's unsolicited.
When parents lash out at non-parents, it's really a reaction to the weight of unrealistic expectations heaped on modern mums and dads, according to parenting psychologist Amanda Gummer.
Child-free people make a convenient scapegoat for those who feel under pressure to be super-parents, she says - especially at a time when many of the social bonds and networks which once were there to assist them have been eroded.
As a result, she adds, many will feel defensive about any commentaries on their parenting style.
"I don't think the media helps," she says. "You have all these self-help books and all these gurus. Parents are feeling under pressure and under scrutiny.
"You don't live next door to granny any more. You're not used to interfering family members giving you advice."
Child-free people may never know what it is like to be a mother or father - but like anyone, they are capable of empathy towards parents and children alike.