Iran's Revolutionary Guards seized the three boats last June and arrested eight British crewmen, accusing them of straying into Iranian waters in the Shatt al-Arab waterway which divides southwestern Iran from Iraq.
The servicemen were handed over to British diplomats but the boats and various weapons and equipment they were carrying are still being held by Iran.
"According to the regulations, equipment which is confiscated in a military operation or dispute, must be handed over to the war museum," said Mirfaisal Baqerzadeh a senior official from Iran's Chief Staff of Armed Forces.
"The British boats are subject to this law and shall not be returned to them," he said on Monday.
Britain's Ministry of Defence has said the sailors were forced by Iran into its territorial waters and has demanded Tehran return the boats and equipment.