The plans for hundreds of building schemes, carried out over a 15-year period in Italy and France, are to be re-examined following the discovery that the engineer responsible never obtained a degree or even sat a professional examination.
Igino Orsini Federici, 43, from Orvieto, north of Rome, is believed to have put his stamp to projects involving churches, historic monuments, private residences and commercial premises.
According to Italian media reports, he carried out work for the national railway and motorway corporations and designed the reinforcement of one of the bridges over the Seine in Paris.
Of particular concern is the fact that Orsini Federici carried out much of his work in his native Umbria, an earthquake region. He is said to have certified scores of structures against the risk of seismic damage after the earthquake that struck parts of the region in September 1997.
Last Friday, the Umbrian authorities denied a report that Orsini Federici had also been in charge of a ?12 million (US$22.53 million project to strengthen the vast rock, riddled with caverns, on which Orvieto stands.
A member of one of central Italy's most illustrious families, Orsini Federici returned from university in Rome in the 1980s claiming to have obtained a first-class degree. In fact, as he admitted to prosecutors in a voluntary statement last week, he only ever passed one of his university exams.
His stamp -- the guarantee that he was a member of the engineers' professional body -- was that of a contemporary who really had qualified, but then never went into practice.
Orvieto's borough engineer discovered the ruse after noticing a minor discrepancy in some documents. The mayor, Stefano Mocio, ordered further inquiries to be made, and then referred the matter to state prosecutors who are investigating Orsini Federici on suspicion of various offences, including fraud.