I am sitting in the community hall of a small Oxfordshire village in a state of some shock. Around me, an audience is applauding a singer who has just delivered a song repeating appalling anti-Jewish prejudices from the Middle Ages.

To be more specific, Alasdair Roberts, a Scottish singer and guitarist, has just sung a version of "Little Sir Hugh" in the village hall as part of the Towersey Folk Festival, a festival which supports 'Folk against Fascism'. This "ballad" tells how young, innocent and good Christian Hugh was murdered by the Jews of Lincoln.

Except that he wasn't, because this is one of the notorious mediaeval 'blood libels' against the Jews, alleging ritual murder of Christian children for religious purposes. Of 90 Jews arrested for alleged involvement in the death of 'Hugh of Lincoln' in 1255, 18 were executed (with the King seizing their property). Countless others suffered pogroms as a result of these lies being spread, so it is something more than a harmless ditty. Of course, we don't expect songs, traditional or otherwise, to be historically accurate, but this song is thoroughly unpleasant.

It would be unfair to single out Alasdair Roberts; the song has a long pedigree, being one of the ballads collected in earlier centuries by Bishop Percy and by Child; versions have been performed by many respected singers in the past, although Alasdair's version did seem particularly unambiguous.

For example, Steeleye Span's version of Little Sir Hugh doesn't even mention the Jews, but attributes the murder to a 'lady gay'.

I tell myself that the audience are applauding the musicianship and not the lyrics. Nonetheless, I am unable to sit through any more of this performance and leave, deeply troubled.

In the days and weeks following, I run my feelings over and over in my mind. Am I being unreasonable? I am normally quite critical of Jews who see anti-Semitism where none exists, although I do understand the historical reasons for that anxiety, and my own experience tells me that we must never tolerate discrimination and hatred.

I reason with myself that I sing 'The Greenland Whale Fishery' while being opposed to whaling in the current world. But I think it is different. There are no laws outlawing a vivid description of the hardships of an old industry (when no one was aware of conservation issues), whereas if you repeated the contents of 'Little Sir Hugh' as a public speech, you would arguably be facing prosecution for spreading race hatred. Furthermore, the blood libels are still believed and used to justify hate and persecution of Jews in some overseas countries, if not in Britain.

The song is on Alasdair's latest CD, which has been well reviewed and which features other excellent folk musicians. Emily Portman, a personal favourite among the younger generation, duets with Alasdair on this one. Emily and Alasdair both sing other ballads about murders but in most we do not associate the murderer explicitly with a specific racial group; the archetypal characters are individuals representing general, if undesirable, human traits such as cruelty or revenge.

According to a discussion on the fRoots forum about Folk Music, Racism and Political Correctness, in the booklet accompanying the CD. Alasdair states "my reasons for singing it, are in no way anti-Semitic; I felt it important to mark the fact that such sentiments once existed, and indeed, continue to exist, in the so-called civilised world…". It is reassuring to know that no offence was intended, but this doesn't make it acceptable. You might as well sing Nazi marching songs because they are historical, or 'because such hatred still exists'.

Does anyone in the mainstream folk movement sing songs accusing Black men of raping White women or that rejoice in a lynching? Such songs existed in the Southern States but are nowadays confined to the lunatic fringe of 'White Resistance Music'.

The discussion is not new. For example, the arguments for and against singing the song are well rehearsed in a discussion dating from 2001 on the Mudcat Café forum. However, our social context and understanding changes. I started work in the seventies when racial discrimination was commonplace and often overt; thankfully we've moved on.

Apparently, Alasdair was uncertain about including it on his record; I think he reached the wrong conclusion. This song may have a place in academic treatises about anti-semitism in popular culture, not in being performed for entertainment (and profit).

24 hours after Alasdair's performance, I am in the same venue listening to Klezmer inspired music from Lebedek. This is followed by Coope, Boyes and Simpson, whose set included one of the most moving songs about the holocaust: A Hill of Little Shoes.

The audience applauded both: that's what we do, it's traditional.