Prime Minister Mariano Rajoy's government is looking at the legal viability of the package of measures planned in response to recent complaints and actions by Gibraltar, Spanish officials said Monday.

The Spanish plan was announced after Gibraltar sent the European Commission a report about border checks that have caused motorists lengthy delays.

Spain says it will not go back on the border control measures and has expressed concern about the dropping of 70 huge concrete blocks by Gibraltarian tugboats to create an artificial reef in Spanish waters near the Rock.

Imposing a 50-euro ($66.25) entry and exit fee, as well as implementing a plan to fight tax fraud, are among the measures being weighed by the Spanish government.

Some 6,700 Gibraltarians live and have an address in Spain but do not list it as their tax residence.

The government is examining the legal aspects of the measures and trying to determine the European Commission's position, officials told Efe.

Implementation dates have not been set for the measures, but they will be enacted as legal opinions come in, the officials said.

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