Israel's foremost authority on passion provoked a heated Valentine's Eve debate this week when he told a London crowd that monogamy was old-fashioned and highlighted the similarities between the lyrics of love songs and the comments of murderers.

Professor Aaron Ben-Ze'ev, president of Haifa University and one of the world's only academic experts in emotions, said that as with Communism, there were many victims of "romantic ideology".

Speaking at a British Friends of Haifa University event to raise money for those affected by the Carmel Forest fires, he said: "You see this romantic ideology in films, on TV and in poems - 'we'll be together forever', or 'you are my one and only'.

"People say 'what a great love', but then they look at their lives and see a great difference. They believe there is something better out there, which is not necessarily so. Now is the best and worst time for love, because we have so many choices, but we can't be satisfied with our lot, and this makes us miserable." Questioned on his work by former Cosmopolitan editor Linda Kelsey, Professor Ben-Ze'ev rejected the idea that love could do no evil. The author of several books and papers on the subject, he said he had found parallels between love songs and what was said by men who killed their wives.

"At the time of the murder there is no love, just rage and hate, but a week or month before they are extremely in love with their wife," he said.

Professor Ben-Ze'ev, currently working on a book about romantic compromises, answered audience questions on everything from the value of marriage counselling to what love was and whether online romances could replace real-world relationships.

But most of the questions came in response to his claim that it was possible to love more than one person at the same time. The professor said that, just as in the intellectual realm, people had discussions with many others, the suggestion that one person could satisfy all needs was old-fashioned.

As extramarital sex had become less shocking, the notion of monogamy could be replaced with "parallel relationships".

But he acknowledged that while such relationships made sense, they remained "difficult from an emotional point of view. It's easy for people to have other lovers - but not to consider their partners doing it," he said.

Ruefully, the professor admitted, however, that while he was an expert on love, his wife said it was "only from the theoretical point of view".