The hauliers were stopped by police as they arrived at the Adriatic port of Bari, southern Italy, from Greece.
The drugs were discovered in the back of a lorry bound for Lancashire during a routine check by customs officers and members of the Guardia di Finanza.
A video released by the Guardia shows officers unloading the white packages, wrapped in black plastic, stashed in between boxes of breadsticks.
Police said the heroin was of an exceptionally high quality and would have a street value of around £16 million.
Italian paper Corriere del Mezzogiorno said the drivers were a 32-year-old Scotsman and a 42-year-old Irishman. They have not been named.
A spokesman for the Foreign Office said today: "We can confirm the arrest of two British nationals on Monday, 26 November in Bari, Italy."
The drivers have been remanded in custody in a local jail and the lorry and drugs seized by customs officers.