Want to be your teenager's "friend"? Forget it, learn to take their hostility and set clear boundaries. Otherwise, writes Kathryn Holmquist , it could all end in tears - most probably yours

Over Christmas, a friend of mine was trying to control her rowdy brood of youngsters at a family gathering, when her own father said to her: "Do they know the meaning of the word 'no'?" Ouch. My friend wanted to reply: "All I ever heard from you was 'no' and I'm not going to limit my children the way you limited me". Instead, she said nothing and got up from the sofa to make a pot of tea.

If you want to get any group of parents talking, mention the "no" word.

Elsa, anticipating the day when her girls will be teenagers, routinely says "no" for no particular reason, except to get them used to the idea. Jane, the mother of a teenage daughter, has never used the word no in her life. "I'm part of the yes generation," she jokes.

And boy, is she sorry. Her daughter hasn't been speaking to her for the past three weeks because she put her foot down and insisted on maintaining an 11 p.m. curfew over the Christmas holidays. "I always thought that my daughter and I were best friends. She's treating me like I'm the enemy. I keep telling her that I'm only trying to keep her safe, but she won't buy it," says Jane.

Her daughter is acting like a tantrum-prone toddler who isn't allowed a new toy every time the family goes shopping. "A few years ago, I couldn't say no to Pokémon cards. I really feel like I'm trying out the word for the first time," admits Jane.

Elaine, a mother involved in a women's group in a working-class area of Dublin, had to have the police called to her house before she learned to say "no". When her children's father left, family life became chaotic. Elaine was out working, the children were coming home at all hours and Elaine constantly felt guilty. Her children had lost so much that she didn't have the heart to draw limits on their behaviour. When her own son began threatening her with physical violence and using the family home as a drug den, Elaine had to get a barring order.

It was the first time she had ever really said "no". The son is back home now and they get on well, she tells me.

Boundaries, when they are too limiting, can create rebellion. The angelic Charlotte Church has shocked the world by becoming a bad girl, firing her mother as her manager, taking up smoking and choosing an "inappropriate" boyfriend. All teenagers want to fire their mothers as their managers, but few can achieve this. Give me a maid, an expense account and my own flat and I'll be happy, the average rebellious teenager believes. With Church, the only difference is that she has actually managed it.

Give any child an overly disciplined regime, where performance is equated with love, and they'll do the same thing. Hats off to her. It must have become infuriating having to be a sweet-voiced angel while all your friends were having a real life.

Church is an example of what happens when discipline goes too far. The "no" word is meant to protect and nurture growth rather than limit it. Tony Wolf, a psychologist and father of teenagers in London, is an advocate of the "no" word. All teenagers need boundaries, such as "you have to be home by 11", he believes. But he doesn't support imposing these boundaries arbitrarily or irrationally. You and your teenager can sit down and discuss the rule, explore why it's there and even change it, if appropriate. But at the end of the day, rules are rules and it's the parent's job to enforce them.

Over the past four months, I've finally come to understand what Wolf is talking about. I've been surrogate parent to a teenager from abroad, who has been attending secondary school in Dublin. She's not even my own child, yet saying "no" has been difficult. I have tried to be her friend and confidante, but discovered that the stricter I became about curfew times in the interest of her own safety, the less of a "friend" she thought I was. By insisting that she be home by a certain time, I was messing up her life, you understand.

It was a good lesson. I had to have the courage for her to be mad at me..

When she tested boundaries, I had to hold firm, even if that meant facing a sullen face over the breakfast table. I now reckon that every future parent of a teenager should look after somebody else's teen for a while and see how hard it is. It's only now that I can appreciate the agonies that parents of teenagers are going through.

In his indispensable guide, Parent Power: Bringing up Responsible Children and Teenagers (Wiley, £8.99), John Sharry, a counsellor and senior social worker in the Department of Child and Family Psychiatry, Mater Hospital, Dublin, describes the typical situation.

When a 14-year-old boy arrives home after curfew, his father confronts him angrily, demanding: "Where the hell have you been?" The son becomes defensive and tells his father to mind his own business. The conflict escalates until the boy storms off to his room, and the father is left wondering what went wrong.

"Press the pause button" is Sharry's advice. Instead of getting into an argument, the parent should take a deep breath and say: "I'm too upset and angry to talk now. Go to your room and we will talk tomorrow". By doing this, you not only avert the emotional harm, but you teach your child about remaining respectful and calm in a difficult situation.

LATER, have an informal family meeting over a meal or activity and discuss the issues. Rome wasn't build in a day, and neither is a teenager's acceptance of boundaries (especially when the parent couldn't say no to Pokémon cards a few years earlier). Let your teenager express his or her views about the curfew time. Listen carefully, speak respectfully and make an agreement on the best solution.

At the end of the day, the best solution isn't saying: "Okay, come home at 3 a.m. if that's what your friends are doing". It's a bit more complicated than that.

Wolf says that all teenagers need to have the parent's voice inside their heads, repeating the boundaries. They might say: "Be home by 11 p.m. or you won't be going out next weekend". The voice of "the parent within" is how teenagers develop a sense of inner conscience, he argues.

"What will eventually end up as the future independent adult conscience is formed, in part, from the gradually internalised voice of the parents," he writes in his book, Get Out of My Life (but first take me and Alex into Town (Profile Books).

At the very time when teenagers want you out of their lives, they need you more than ever and deep down, they know it.