SPANISH envoys will follow and "monitor" Catalonia's pro-independence president as he visits Scotland on Wednesday.

In a tense diplomatic stand-off rarely seen in Edinburgh before, Madrid officials are understood to be on stand-by to rebut criticism of Spain from Quim Torra.

Spain's new socialist foreign minister, Josep Borrell, has ordered his ambassador to London and consul in Scotland to respond to Mr Torra if he "goes too far" in his remarks about the current constitutional impasse in Iberia.

Diplomats will be watching not just what Mr Torra says but where and when he says it amid a highly complex and disputed set of protocols over the foreign policy role of Catalan leaders.

The Edinburgh visit comes less than two weeks after a diplomatic spat in Washington between Mr Torra and Spain's ambassador to the United States, Pedro Morenés.

Mr Torra had given a speech at the opening of an event on Catalan culture at The Smithsonian in which he referred to colleagues jailed for carrying out last year's independence referendum, which was declared illegal by Spain, as "political prisoners".

Mr Morenés then objected to the term, sparking whistles, cries of "liberty for political prisoners" and a walk-out by Mr Torra.

Digital newspaper El Confidencial reported that Mr Borrell, who is also a Catalan, had told his envoys to adopt what has become known as the "Morenés doctrine".

The paper said Spanish officials would be expected to respond to criticism in the way Mr Morenés did in Washington - but only if the criticism is voiced during public proceedings rather than a scheduled press conference.

Mr Torra arrived in Edinburgh on Tuesday evening ahead of meetings with both Nicola Sturgeon and former Catalan education minister, Clara Ponsati, one of the "exiles" to whom he referred in Washington.

Ms Ponsati, a professor at St Andrews University, is fighting extradition to Spain on controversial treason charges.

Official meetings between two pro-independence leaders of non-sovereign nations are rare. Alex Salmond met the former premier of Quebec Pauline Marois in Edinburgh when both were in office but he did so behind closed doors.