But when my own sons - now 20 and 26 - were born, I had no desire to teach them Hungarian. They were a further generation removed from the Hungarian connection, and in the 70s and 80s Hungary was still a remote Soviet satellite - so what advantage could its arcane language offer them?

Fast forward to the 21st century, and Hungary is a full-blown democracy about to enter the EU fold, and a popular holiday destination. My sons now bemoan the fact that I never taught them Hungarian, as they would love to take their girlfriends to Budapest and chat with their relatives. So I guess I got it wrong ...

Loli Farrell, who is Spanish but married to an English businessman and living in London, spoke only in Spanish to her children Elena and Alan - now in their 20s - while they were growing up. Today they are bilingual. "They have both stayed with my family in Spain for prolonged periods, speaking only Spanish, making native friends and immersed in the culture," says Loli. "It gives another dimension to their lives."

But that wasn't the reason Loli passed on her native language to her children. "I spoke to them in Spanish because I had thoughts and feelings that I knew I could only communicate to them in the language in which my mind works. I wanted to express myself genuinely, so that they could know me as I really am, rather than an English-language version of me."

Her thinking is in sharp contrast to the widely-held beliefs of a generation earlier. My own bilingual upbringing notwithstanding, most parents of that era felt that absorbing more than one language in early childhood would confuse their offspring and be detrimental to their learning. My partner Nick - the son of an English father and Danish mother - remembers the accepted wisdom of the day: "Not only did my mother not speak to me in Danish, but my parents were also both fluent in German and French and they refused to teach me those, too. They felt it would slow down my development in English, that I would get muddled while working out how all the bits fit together."

Professor Tony Cline of Luton University's Centre for Education Studies is a psychologist specialising in language development in children. He says we have revised our image of how the brain works. "We used to think it had a limited capacity, like a milk bottle, and that it was impossible to pour two pints of milk into a pint bottle. Now we understand that our brains are capable of making an infinite number of connections; there is no limit to what we can take in."

He concedes that there might be temporary disadvantages in having a bilingual childhood: "The child sometimes applies the rules of one language to another, and so makes mistakes. But these grammatical 'errors' are trivial and soon outgrown. Any slight delays in language development are more than outweighed by the benefits of bilingualism." These include an enlarged cultural repertoire, the boost to intellectual growth that comes from accessing the literature of different countries, and the self-evident practical benefits in an era of globalisation.

And, Cline points out, there is an equally important social advantage. "Experiments have shown that bilingual children are better at taking the perspective of another person - ie, having more than one cultural 'identity' heightens your ability to put yourself into someone else's shoes. And while the practical usefulness of a language depends on how widely spoken it is internationally, in terms of its broader, more abstract value, all languages are equal."

Multilingual Matters is a Bristol-based publishing firm specialising in books on all aspects of multi-lingualism, and producing a newsletter for bilingual (and trilingual) families around the world. It was started nearly 25 years ago by Mike Grover and his Finnish wife, Marjukka, who were bringing up their two sons in both English and Finnish and found that they were frustrated by a lack of practical advice.

As Marjukka explains, "Flawed research in Wales in the 50s produced quite negative conclusions and the belief that raising children with more than one language would result in them having poor language skills. It wasn't until the 80s that this was discredited by more sophisticated studies in Canada.

"When my children were born, I immersed them from the beginning in Finnish, and while I was sure I was doing the right thing, I wanted to learn more about the business of raising bilinguals. A lot of research had been done on it, but it had no natural 'home'. So we formed MM."

Multi-lingual families are in constant need of guidance, she says, because bringing up children with more than one language can be a real struggle. Some children rebel against the "minority language", which makes the parent who speaks it feel rejected and upsets family relationships. Some parents worry about their children's habit of mixing different languages in the same sentence, or agonise over whether a child's dyslexia or speech defect is caused by their bilingualism. "Multi-lingualism is a wholly positive thing in any child's life," says Marjukka. "But it mustn't become a battleground.

"The 'one-parent, one-language' approach - in which the mother speaks to the children in one language and the father in another - is perfectly acceptable, but rules should not be carved in stone. For example, young children are often embarrassed if a parent speaks to them in a foreign language when they are with their English-speaking friends. It sets them apart from their peers at an age when they like to conform. I was sensitive to this, so although my rule was to speak to my children only in Finnish, I did make exceptions."

In her view - backed up by the experts - it is best to start teaching a child a second language from birth. "Then it is effortless, the languages are absorbed naturally, s if they were one. From the age of three they separate the languages and it takes a more concentrated effort to learn them."

Studies carried out last year in Britain concluded that children who speak two languages do better at school than those who speak only one. Dr Raymonde Sneddon, from the School of Education and Community Studies at the University of East London, was able to demonstrate that far from being confused by using different languages, these children display greater comprehension when reading English. They tend to be in higher ability groups - because the skills they acquire and develop in their language use is transferred to other subjects.

A study in Leicester found that bilingualism improved a child's overall educational performance by instilling a more subtle use of language and better communication skills. Arvind Bhatt, who led the study, said its findings contradicted the controversial comments made in 2002 by the home secretary, David Blunkett, who decried the "negative impact" on society of children growing up with different languages at home and at school.

"Blunkett's view was based on the false premise that children can learn only one language at a time and that learning a mother tongue interferes with English," says Bhatt. "But we found that bilingualism was an asset in the long term, although it can cause some short-term difficulties."

The Grovers' son, Sami, now edits MM's Bilingual Family Newsletter. "It can be frustrating bringing a child up with two or more languages," he admits, "particularly if there is no support network around you. A family has to be patient, listen to the needs of their child and, if appropriate, seek professional advice from experts familiar with research on multilingualism. When nurtured with patience and sensitivity, multiple languages can be source of great wealth for children, their families and society in general."

Now I really feel guilty. I wonder if it's too late to start teaching my kids Hungarian? I've still got an old primer somewhere ...

'My Italian was my gift'
Sara Stowe is an English singer and mother of two

I was brought up speaking English, but I studied in Milan and spoke Italian by the time my son Lewis, now nine, was born. I didn't think of speaking to him in Italian, but when my daughter Harriet was born four years later I was amazed to hear the fluent French of a two-year-old waiting for her sister at my son's school. This child had grown up in a bilingual family, and hearing her set me on the strange enterprise of bringing Harriet up to speak Italian as well as English.

I did an A-level course to brush up on my skills and decided I would always speak to Harriet in Italian. It must have been odd for Lewis but he and I have always sung together in French, so adding another set of sounds was just a continuation of what had been going on before.

Now Harriet speaks good Italian, and after nursery she got a place in the European school in Oxford, a specialist language school. By the age of two Harriet could understand my Italian but would reply in English. At nursery she spoke English until she made friends with an Italian two-year-old and since then she has spoken to me in Italian. I think that if you speak a language fairly well (even if not perfectly) you have a gift to pass on.

'It's all about having fun'
Pascale Gravell was born and brought up in France. She is a mother of five and editor of familiesmagazine.co.uk

The trick to bilingualism is knowing what will work in your family. We have lots of relatives in France so we make a point of spending holiday time with them. Each of my children has at least one cousin of their own age, and they spend hours outdoors playing together. There is no sense of it being about learning - it's just about communication. Each time we come back my children have beautiful accents, as well as the latest slang and funny expressions that couldn't possibly have come from me. Then it's back to their English school and it's all downhill until the next holidays.

I do have a few other tips, though. First, install French TV at home (we're even thinking of cutting off the English TV channels). Second, find your children French friends. Third, enrol them at a French nursery before they start (English) school. We read a lot of story books in French and have a subscription to a fun French magazine.

Although I talk to my children in French at home, I have to confess that they do still speak to me in English. It breaks my heart, but they can speak French and understand it when they need to.