When Alex Salmond published his blueprint for the independence referendum at Edinburgh Castle in January 2012, Spanish and Catalan journalists attended in droves.

Watching the Scottish Government taking its first steps towards its dream of a vote on independence, with the UK Government's acquiescence, clearly impressed the Spanish contingent. That a debate on the break-up of the UK could be conducted with such politeness and respect (superficially at least) contrasted sharply for them with the debate on Catalan independence, where the devolved Catalan government was blocked by Madrid from holding an independence referendum.

That resistance on the part of the Spanish Government was put to the test yesterday, when Spanish MPs voted on a request from the parliament of Catalonia to hold a referendum. The request was expected to be rejected, in view of which the independence vote in Scotland must seem all the more enviable in Catalan eyes.

Even so, visiting Iberians might not be quite so impressed as they once were by the behaviour of the opposing camps in Scotland. A beacon of civility? Sadly it seems less and less so by the day. The speech yesterday by former Nato Secretary General Lord Robertson warning about the global consequences of Scottish independence was highly intemperate.

Thundering like an Old Testament prophet about the "cataclysmic" effects of a Yes vote on the security of the West and how it would delight the "forces of darkness", the one-time Scottish Labour leader succeeded in filing himself and his opinions into the box marked "scaremongering". Whatever the merits of his underlying point, they were obscured by his choice of words. The Deputy First Minister is right about his language doing a disservice to the debate.

Both sides have at times fallen short of the standards they ought to adhere to. It is only a few days since the chairman of Better Together, Alistair Darling, hit back at the refrain that the No campaign has been overly negative about independence, accusing pro-independence supporters of "monstering" those with opposing views. The pro-UK campaign has indeed been responsible for a series of dire warnings about the consequences of independence, instead of focusing on a positive case for the staying in the UK, yet it is also true that those arguing for the UK have often been met with vociferous disparagement from Yes supporters. The SNP have of course been consistent over a period of decades in couching Scotland's relationship with Westminster in the most negative of terms, and continues to do so. Pots and kettles.

A robust, passionate public conversation is what Scotland needs. Scots can be proud of the fact that the debate about independence has for much of the past two years been conducted by both sides with dignity. If it is allowed to slide into jeering, intolerance and hysteria, however, it will not only disappoint international observers who look to the UK constitutional debate as an example to their own governments, but will taint forever the crucial vote itself.