Police in San Sebastián have arrested 56 individuals who are thought to have obtained driving licences for up to 2,000 people.
They are also said to have forged residence cards, enabling them to take tests on the candidates' behalf.
The group, who are said to be mostly of Pakistani origin, also took driving theory tests passing as others.
By charging up to 3,500 euros per driving-test candidate, the group are said to have amassed around six million euros between them.
Investigations began in April in the province of Guipúzcoa, when the residence card of a test candidate of Pakistani origin was found by driving examiners to have been forged, carrying the photograph of the man presenting himself for the test with the name and date of birth of another person.
A month later, another man accidentally handed in his copy of the group's 'cheat sheet' instead of his exam paper after a driving theory test.
Although they were based in the Basque Country, the organisation had customers all over Spain, mostly of North and Sub-Saharan African or Pakistani origin.
Of the 56 people caught, 47 were from Pakistan, four from Morocco and five others from Ghana, the Ivory Coast, India, Mali and Gambia.
Some of the arrests were made in Valencia, Barcelona and Palma de Mallorca.
