Spanish Prime Minister Mariano Rajoy's government is considering adopting different measures in response to recent complaints and actions by Gibraltar, which sent the European Commission a report about border checks that have caused motorists lengthy delays.

Government sources informed Efe about a series of measures that Spain is contemplating.

The plan, drawn up with input from various government ministries, reviews the events leading up the dispute and refers to the border controls that Spain has adopted in recent days and which the British overseas territory maintains are interfering with the "right to freedom of movement of EU citizens."

Spain's Foreign Affairs Ministry, however, noted that Gibraltar is not part of the Schengen Area, or EU Customs Union, and therefore the border controls at the Rock "are unavoidable" for the Iberian nation.

It maintains that the controls are necessary to avoid illicit traffic and, in that regard, the document states that a significant 213 percent increase in tobacco smuggling was detected between 2010 and 2012.

The controls, according to Madrid, are "random" and therefore affect Spaniards and Gibraltarians alike.

One packet of measures will be aimed at environmental protection, the sources said, noting that Spain's Agriculture, Food and Environment Ministry filed a complaint with Spanish prosecutors about the dropping of 70 huge concrete blocks by Gibraltarian tugboats to create an artificial reef in Spanish waters near the Rock.

Additional tax measures also are under consideration, including a plan to clamp down on some 6,700 Gibraltarians who live and have an address in Spain but do not list it as their tax residence.

Gibraltar is a territory of 5.5 square kilometers (2.1 square miles) at the entrance to the Mediterranean Sea. It has been held by Britain since 1704 and became a British Crown Colony in 1713 in accord with the Treaty of Utrecht. EFE