The trio were held with two Spaniards in an operation carried out in Granada and the Basque province of Guipuzcoa near Spain’s border with France.
Detectives said 1.2 tonnes of cocaine had been seized along with an underground cannabis plantation.
They described the Britons as members of a “criminal organisation dedicated to international drugs trafficking.”
More details of the drugs seizures and arrests are due to be revealed later at a press conference at Spanish National Police headquarters in Madrid.
The cannabis plantation is understood to have been discovered in Zarautz, a coastal town near the beautiful Basque city of San Sebastian which is a famous surf destination and home to a stunning two mile sandy beach.
A police spokesman said: “The gang was based in the UK as well as in Spain.
“The drugs seizure constitutes one of the largest ever intercepted on Spanish soil.”