Having been a single parent for almost all of my daughter's life, I can honestly say I've probably been forced to ascribe to the "benign neglect" school of parenting – not through choice, but necessity. All parents face hard judgment calls, so I've been watching this debate about when you should or shouldn't leave your child on his or her own at home with interest. It's been raging on Mumsnet, the parenting site, for a while. And it's cropped up in the Daily Mail recently. This summer, the Children's Legal Centre called for clarification of existing law, which fails to specify at what age children can be left on their own. Charities have predicted that more than a million children are left alone over the summer hols because childcare costs are too high for some families, putting some potentially at risk of prosecution.

The government says children have different levels of maturity and responsibility at different ages. What does that really mean? A friend who works for the NSPCC shocked me when she said there is no legal level and it's all about choice. Most people seem to think the law stands at 12, but actually it all boils down to whether they are in a "safe place".

While leaving a toddler alone in a cot with a bottle of milk wouldn't go down well with the authorities, for obvious reasons, on the other hand Madeleine McCann's parents were forgiven by some for leaving a three-year-old and two-year-old twins alone in a Portuguese resort room.

A few months ago, I left my eight-year-old alone for 10 minutes in my flat while I nipped to the shops to get some milk – OK, wine. I asked her to come with me. She was watching TV and the prospect of getting shoes on and missing her shouty American show on Nickelodeon was apparently too much to bear.

I quickly ran through the "what ifs". If anyone rings the doorbell, don't answer it. Here's my mobile in case of an emergency. I left the flat, found myself half running to the nearby shop, a creeping sense of guilt rising in my guts. I berated myself for not telling C not to eat anything. What if at that exact moment she was choking to death on a grape?

I got back to find my daughter was still sofa-ridden, her eyes fixed on the TV. She didn't even acknowledge my homecoming.

I needed a glass of wine after that. But am I right to beat myself up? If my friend's reactions are anything to go on, I probably should be. A friend with a 10-year-old child (and a husband) paled at the suggestion that she left the house without her son. "What if something happened to me?" she whispered. "Or him?" Another proudly told me, she never ever let her child out of her sight, even in enclosed soft play areas. "You just never know," she said, shaking her head, quoting a story she once read of an 11-year-old using a supermarket loo on her own and then getting raped.

As far as my daughter's concerned, we both need reasonable time alone. My brother's 20-year-old girlfriend is terrified of walking alone down a street after sundown, because she was rarely allowed out at night before she left for university.

I've been letting my daughter walk to school with a group of friends most mornings – a decision my peer group mothers have expressed surprise at. It's a 15-minute walk and involves crossing two major London roads. She's with three 10-year-olds and a fellow classmate. Are they old enough? The school's policy says eight is the minimum age for solo walking. Three out of the five of the walking gang (all girls) have parents who are single working mums. How much has that swayed their decision to give their child that responsibility? Probably quite a lot.

I know it is a risk letting her walk: I feel that every time our lips brush goodbye. But I get an hour extra in the morning to work or even go to the gym, and she gets a sliver of preciously savoured independence. It works. The benefits outweigh the risks.

If anything happened to her no one would blame me as much I would myself. But surely a parent's job is not to solely keep her safe, but teach her to manage on her own? I don't want her to think we live in a bad world with danger at every corner. We don't. I believe what kind of woman she'll become directly correlates with what she's been allowed to do as a child. I want her to confidently work out that safe route herself, so one day when my hand is no longer here to hold, she'll feel secure in her own judgment and know security comes from within.

• This article was amended on 16 November 2009. The original referred to Madeleine McCann's parents as leaving their children alone in a Spanish resort room. This has been corrected.