The best-selling author of Baby Love and The Mighty Toddler argues that a weekly child-minding commitment is a big ask of grandparents and suspects many feel secretly resentful about doing it.

''I'm prepared to do quite a bit but I'm not prepared to mind children while people go out to work,'' said

Ms Barker, who regularly picks up her two grandchildren from school and babysits.

''It's a huge commitment when you're doing even one day a week … we really don't have the physical and emotional strength we had when we were raising our own children. A day with a toddler is a very long day.''

Ms Barker said she heard ''a lot of complaints'' from grandparents who felt put upon by their children. ''There is resentment about what children expect their parents to do. Many grandparents present one face to their children and one face to their friends.''

As more women return to paid work after having children, grandparents are increasingly called upon to help out with childcare, either because official childcare is too expensive, parents feel their children are too young for long day care or because it's considered quality time for grandparents and grandchildren.

There are nearly 300,000 Australians aged between 50 and 74 caring for their grandchildren, and a third of these are also employed in paid work, according to National Seniors Australia.

Ms Barker believes many grandparents who agreed to a child-minding arrangement in the first flush of excitement of having a grandchild come to regret it as the reality of the regular commitment sinks in.

''They'd rather not be doing it - but I doubt many people would publicly acknowledge this,'' she said, adding ''there are some people who love it''.

The manager of Relationships Australia NSW, Lyn Fletcher, said grandparents considering a regular child-minding gig should suggest a trial first, and a regular review of the arrangement if they then proceed.

''You need to know what you're getting yourself into and that your adult child understands what the limits are for you,'' Ms Fletcher said. ''If you find it too much you need to say, or if you want to jump into your caravan, or you get sick, you need to know they've got alternative arrangements.''

Ms Fletcher said adult children needed to think about grandparent day care ''on a business-like basis, otherwise grandparents are being used as a dumping ground''.

Judy Payne had no qualms about looking after her grandchildren when her daughter and daughter-in-law went back to work. ''These days when people have to go to work [for financial reasons] it's up to family to help each other out,'' she said. Mrs Payne looked after her first grandchild five days a week until she went to school, so her daughter, a single mother, could work. Later she minded her daughter-in-law's children one day a week each.

Mrs Payne said it was tiring, but worth it because of the opportunity to have one-on-one time with her grandchildren.

''I would put up with [being tired] to have that time together … I have built up a very strong relationship with [my eldest granddaughter], which I wouldn't have done if I hadn't looked after her. The advantages outweigh the disadvantages.''

However, she did warn: ''You've got to be careful not to become a slave to your children.''