A letter in a local paper days before the Scottish Parliament opened last month reminded the newly-elected MSPs that "this country's national religion is Protestant and Presbyterian and the Scottish Parliament is duty-bound to reflect this fact".

Sectarian sabre-rattling maybe, but for some Scottish Catholics it was an eerie echo of how the first prime minister of Northern Ireland, James Craig, infamously called for the Stormont government to represent a "Protestant state for Protestant people".

No coincidence, perhaps, that Scottish Catholics were equivocal in their support of the 1979 home rule referendum - the unvoiced fear being that a devolved Scotland would be a "Protestant country" with no UK government around to enforce equal opportunities.

By the time of the next devolution referendum in 1997 that fear had receded - to the extent that Catholics were as likely to support home rule as Protestants.

A number of events over the last few weeks in the newly-devolved Scotland have reopened the weeping sectarian wound and threaten to tarnish the much touted image of a new, optimistic and forward-looking country.

The ex-lord provost of Glasgow, Mr Bob Gray, made an official complaint to Lord David Steel, the presiding officer of the Scottish Parliament, asking why no Catholic children were invited to join schoolchildren in the procession down Edinburgh's Royal Mile that marked the opening of the parliament on July 1st this year. Lord Steel apologised, saying it was "an oversight".

Meanwhile, an editorial in a magazine run by the Free Presbyterian Church condemned the late Cardinal Basil Hume for exercising his "influence" in Scotland. And members of the Church of Scotland have urged MSPs to scrap plans for multi-faith prayers in the new parliament and to use only Presbyterian prayers.

But just as these incidents were being treated as "blips", a speech to mark the opening of the biggest arts festival in the world - the Edinburgh Fringe Festival - last Sunday had it that Scotland was so rife with anti-Catholic bigotry that it was like "Northern Ireland without the guns and bullets".

Quite a dramatic flourish, even by Edinburgh Fringe standards. The speaker was the prominent and highly-accomplished contemporary composer, James MacMillan. A Glaswegian Catholic, MacMillan, aged 40, drew on his own childhood experiences of being spat upon on the street because he was wearing a Catholic school blazer. His speech was titled "Scotland's Shame".

"In many walks of life," he said, "in the workplace, in the professions, in academia, in the media, in politics and in sport, anti-Catholicism is as endemic as it is second nature . . . Scotland is guilty of sleep-walking bigotry. Because of this, most Scottish Catholics learn at an early age that the best mechanism is to keep one's head down. Try not to attract attention to the fact that you are a Catholic - it will only annoy them."

On the same day that MacMillan made his speech, an executive of Glasgow Rangers football club, Mr John Greig, was photographed by a tabloid newspaper allegedly leading renditions of anti-Catholic songs. This incident comes only weeks after a Rangers' vice-chairman and senior Scottish Tory, Mr Donald Findlay, was forced to resign from the club having been filmed singing virulently anti-Catholic songs. In Scotland, anti-Catholic is synonymous with being anti-Irish.

Similarly, the Scottish national football coach, Mr Craig Brown, recently faced calls for his resignation after a newspaper alleged that he, too, had sung rabidly sectarian songs.

"Donald Findlay is not a one-off," said MacMillan in his speech. "To believe this is self-delusion. Our workplaces are jam-packed with people like Donald Findlay. These men have a responsibility and it's people like them - professionals, doctors and lawyers - who are doing the damage. I hope Donald Findlay realises exactly where his prejudices have led."

He went on to mount a strong defence of Catholic schools (there have been recent attempts in Scotland to abolish them): "Fear and alarm are spreading in the Catholic community over what is perceived as an ideologically-motivated campaign against Catholic education which seeks to remove a Catholic voice and public presence from Scottish society."

The response from other prominent Scottish Catholics to the speech was ambivalent. While Prof Tom Devine, of Aberdeen University, said it was "over the top", Mr Tom Carberry, of the Scottish Catholic Communications Commission, commented: "While the situation of Catholics in Scottish life is immeasurably better than years ago, it is not as good as it should be. There is still not genuine parity of treatment and attitude across the board."

To the casual observer, religious bigotry in Scotland comes down to sporting sectarian rivalry between Glasgow's two main football clubs, Rangers and Celtic, but Mr MacMillan's speech - which was widely reported by the massive media presence in Edinburgh for the festival - has drawn attention to an aspect of Scottish life which has been largely ignored, or dismissed as harmless or minor.

Commentators have drawn attention to violent acts against Catholics in Scotland, including murder, which have been portrayed in the media as instances of "football hooliganism" and not of sectarian hate.

Although sectarian attitudes patently persist in Scotland, according to the evidence available there does not appear to be any systematic discrimination against Catholics in terms of education, income and employment - although this may be because there has been little or no research in the area. Indeed, the next Scottish census will not contain any questions about religious affiliations - in the UK, only Northern Ireland's census forms pose the question.

Although such "sectarian head count" questions are scorned by liberals, sociologists deem them vital as a measure to monitor possible cases of discrimination on the basis of religious background.

Mr MacMillan's articulation of "the discrimination that dare not speak its name" has prompted many Scottish Catholics to speak out in support. "I left Scotland 26 years ago to escape precisely the bigotry described by James MacMillan. I returned eight years ago and things were, if anything, worse. So I left again. If anti-Catholic racism vanished, returning Scots would double or perhaps triple the population," ran one of the typical letters to the local newspapers this week.

Another contributor, accepting that "anti-Catholic feeling is still present in contemporary Scottish society", referred to "the shame of how my fellow Scots wear their anti-English prejudices - it's racism".

There have also been many calls for the Scottish Parliament to pass an anti-religious discrimination law. At present the law only allows for redress through the courts on the basis of racial discrimination. Whatever about legislation, as the Scots busy themselves travelling around the world, opening new embassies, James MacMillan's criticisms represent one piece of excess baggage they could well do without.