A bad idea has made an unwelcome return to the spotlight. Two years ago, the Association of University Teachers proposed a boycott of Israeli academic institutions in protest at the treatment of the Palestinians by the Israeli state. This resulted in protests from writers and academics around the world, including 21 Nobel prize-winners. The union eventually overturned the resolution.

But yesterday, at the annual conference of the successor to the AUT, the University and College Union, lecturers once again found themselves debating a motion calling on UK academics to "consider the moral implications of existing and proposed links with Israeli academic institutions". Despite the appeal made by the new general secretary of the UCU to reject the motion, it was passed by 158 votes to 99. The motion will now be put to the wider union membership to bring it into force.

Let us be clear why a boycott is a deplorable idea. The purpose of the embargo is fatally unclear. The motion condemned Israel for its "denial of educational rights for Palestinians by invasions, closures, checkpoints, curfews, and shootings and arrests of teachers, lecturers and students". But what has this to do with Israeli universities who would be the target of this boycott? Some Israeli academics have worked hard to oppose the excesses of their Government in the West Bank and Gaza. What good does it do to punish them in this manner?

On a philosophical level, boycotts do not sit easily with the principles of universities, which are built upon the foundation of the free exchange of ideas. But it is on a pragmatic level, as we report today, that this idea could do the most damage. A boycott could actually hurt those that it purports to support. Many Palestinian students are eager to study in Israeli universities, but are thwarted by the draconian travel restrictions imposed by the Israeli army. An international boycott would do nothing to help such students fulfil their ambitions. And if it caused Israeli academia to recede into resentful isolation it could do them positive harm.

We also need to examine the motivation of those who voted in favour of this motion yesterday. There is a strong whiff of gesture politics. Although this motion might have made those who backed it feel virtuous, a boycott will not discomfort the Israeli government. On the contrary, it will offer Israeli propagandists a convenient excuse to accuse British academics of bias whenever they produce work that reflects the Israeli state in a negative light.

An academic boycott would be a self-indulgent distraction from the real issues. The rank-and-file members of the UCU should demonstrate the good sense that their delegates lacked and vote down this proposal.