A generation ago, most parents began toilet-training their toddlers around their second birthday. Today the average age for completing training in the UK is nearer 3. There is no physiological reason for this delay, it’s a Western phenomenon. In developing countries most children are trained by 18 months.

Since around eight million disposable nappies are thrown away each day to be buried in landfill sites where they could take many years to decompose, it is surely common sense to try to reduce the time that children spend in them. By returning the toilet training age to nearer 2, our nappy waste could be cut dramatically. Yet this is a course that much of the childcare industry, the Government and most parents seem reluctant to explore.

Although the Government backed the Real Nappy Campaign to encourage parents to ditch disposables for reusable nappies, it doesn’t want to get involved in encouraging parents to train earlier. A spokesman for the Department for Children, Schools and Families said: “This is a matter for parents and we trust them to use their judgment in making decisions about what is best for their child.”

So why is it taking us so much longer to get our kids out of nappies and into knickers? Technology is partly to blame. The first rise in the training age coincided with the arrival of the automatic washing machine. It wasn’t until disposable nappies hit the mass market in the UK in the early 1970s, however, that the toilet-training age really started to rise. Parents put it off because they preferred the convenience of the disposable to a few weeks of “accidents”.

This period also coincided with the growth in the number of working mothers. As our lives began to revolve more around convenience there was a gradual shift in thinking towards training.

“People now have very busy lifestyles in which they and their children are often in a car or at public locations where toilets are not rapidly available,” says Dr Nathan Blum, a paediatrician and expert in childhood toilet training.

“Our culture is different now to what it was 30 years ago,” says June Rogers, a specialist paediatric continence adviser and director of PromoCon, a charity devoted to improving the lives of people with bladder and bowel problems. “Then, grand-parents played a much bigger role in family life. You’d find Grandma telling parents, that ‘it is time to take him out of nappies’. Now the approach is much more laid-back, with the focus on waiting until the child shows that he is ready.”

The idea that you must wait for the signal from your child that he is ready to be trained is now ingrained in our society. Most health visitors will tell you to wait for the initial signs: your child telling you when her nappy is dirty, she can pull her pants up and down and is happy to sit.

And, whereas nurseries often used to refuse admission to children over the age of 2¾ who weren’t toilet-trained, under the Disability Discrimination Act they now can’t do this.

Plus, all the big disposable nappy manufacturers produce nappies big enough for children well over the age of 2. Pampers has nappies for children of between 11 and 25kg and Huggies produces nappies that fit children of 17kg plus. To put this in perspective, the average weight of a four-year-old girl is 16.25kg and the average weight of a four-year-old boy is 16.60kg.

The nappy manufacturers, however, deny that they are encouraging parents to keep their children in nappies for longer, and say that they are responding to consumer demand.

“We do not recommend that children stay in nappies any longer than they need to,” says a spokes-person for Huggies manufacturer Kimberly-Clark. “We publish lots of useful advice on our website for parents, including a kit and hints on how to spot the signs that a child is ready to begin toilet training. Children develop in different ways at different stages and our priority is to cater for all the varying needs of our consumers.

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