The task of removing graffiti is estimated to cost the local council some €500,000 a year, and in recent days 'tags' have appeared on several national monuments in the city.

"This is a serious matter and, although it is not new, it had not happened with this intensity and lack of taste," said the mayor, Manuel Machado, told Lusa. "Even when the [Maoist] MRPP entertained itself scribbling slogans on walls, at least one could note a certain aesthetic sense. What we see today is a mess.

"It's unacceptable, it should be punished, it is a crime."

Machado said that a video surveillance system was "one of the tools" that could be used to combat the problem.

"We shall resort to the legal instruments, within existing rules, to neutralise this kind of undesirable behaviour that damages the public interest," he said, when asked about whether CCTV could be introduced in Coimbra's upper town, where the old cathedral and several other national monuments are to be found.

Machado cited the São Salvador church as one of example of a monument whose façade has become covered in graffitied phrases and tags.

"It is one of Coimbra's oldest churches, used for most royal weddings of the first dynasty," he said. "The Machado de Castro Museum is a jewel that is dilapidated by this kind of vandalism. Even the sculptures by Rui Chafes [in the Jardim da Sereia gardens], after the council invested more than thirty thousand euros in restoring them, the next day were vandalised by graffiti in bad taste."