A new study says parents' efforts to bring up well behaved children who eat healthily and follow a strict routine are being undone by grandparents who break their own children's rules.
The study of 2,000 parents, carried out on behalf of comedy film Parental Guidance, found that youngsters get fed what they want when they want, are allowed to watch whatever they want to on television, and stay up later than their normal bedtime when they stay at their grandparents' house.
The study found 83 per cent say their children are regularly spoilt by their grandparents with plenty of chocolate or cakes the most common treat.
More than a third claim that their children are allowed to stay up past their bedtime at their grandparents and get away with not eating any of their lunch or dinner. They're also allowed to get away with answering back and being cheeky.
Commenting on the survey, ITV's This Morning agony aunt, Denise Robertson, said: "Grandparents are turning their grandchildren's parents into the 'bad cop'. An over-indulgent grandparent is selfish.
"They are satisfying themselves, they are buying love for their own ends. They are not thinking about the welfare of the child.
"Just throwing the parents rules out of the window is a completely unfair thing to do."
In fact, one in four parents find it such a struggle to get their children to behave again when they return home that they refuse to let youngsters stay overnight with grandparents at all.
And more than one in five admitted rowing with their parents or in-laws because they spoil their children too much.
Of course, grandparents have always spoilt their children, but according to Denise, the fact that modern financial pressures have put an expectation on grandmothers, especially, to step in as unpaid childminders while their daughters go to work might actually make them resentful – and thus enforcing rules could be seen as more trouble than it's worth.
Denise – who has eight step-grandchildren and four step-great-grandchildren - explained: "When you are a parent you are very conscious of the fact that your child's welfare, health and character is your responsibility.
"But when you are a grandparent, even though you love them just as much, the responsibility is on someone else's shoulders. It's easier to break the rules. And grandchildren are very clever. When they look at you with that appealing face then it's very difficult not to give in to them.
"And why not? Grandparents think, 'As much as I love my grandchildren I don't like the expectation that I am expected to be a parent again because my daughter has to go to work'.
"Grandparents think they've earned their free time but because of the recession they are expected to become parents again."
One way this expresses itself is by deliberately breaking their offspring's rules, she said. "There is a screamingly funny scene in Parental Guidance where the children are not allowed to have cake so the grandmother gives them some.
"The mother arrives back to find the children covered in chocolate cream.
"The little girl says, 'You lied to me, chocolate cake IS better than yoghurt'.
"The point of this is that mothers should realise that there is room for a little bit of cake. If the mother never lets them have cake, it is going to be the one thing they are going to want."
It is examples like this that can cause conflict in families and often leads to a war of attrition.
The only way to resolve this is with give-and-take and that age-old tool: communication.
From a grandparent's point-of-view, Denise advises: "Sit down with your children and agree some basic points of things that are important to the parents. If you think they are being unreasonable then you can argue about them but they must be talked through."
And she has this advice for mums and dads who believe their children's grandparents are breaking their parental rules: "If you think they are being too harsh or too soft, then don't approach it in a judgmental way. Say, 'You know how much I care about little Johnny, I'm not sure about this but do you think it might be better if they weren't allowed to swing from the ceiling'.
"It's easy to lose your temper at the end of a tiring day, so pick your moment. "If you pick your children up and you feel they have been indulged too much, don't have it out there and then. Make a time to sit down and talk it through properly, away from the heat of the moment."
TOP TEN WAYS GRANDPARENTS SPOIL THEIR GRANDCHILDREN
• Give them chocolate or cake
• Let them stay up late
• Let them off if they don't want to eat all of their lunch or dinner
• Let them eat whatever they want
• Let them eat their lunch/dinner in front of the TV
• Let them do whatever they want
• Don't tell them off if they are naughty
• Let them eat whenever they want
• Let them watch TV shows that I usually say no to
• Put up with them talking back
• Parental Guidance, the family comedy film, is out now on Blu-ray and DVD