MADRID (Agencies) The British government yesterday levelled energetic criticism against the Spanish authorities for the alleged arrest of two Gibraltarians in the sea that surrounds the Rock, an action Britain called 'intolerable and illegal'. Secretary of State for European Affairs David Lidington said he was "shocked by the disgraceful behaviour of the Spanish Guardia Civil" who he said detained the nationals in British Gibraltar territorial waters and transferred them to Spain on Friday." "The government will be making it clear to Spain that such action, on the part of the law enforcement agencies of a EU Partner and NATO Ally, is intolerable and unlawful," he warned. The move comes amid a row over fishing rights between Madrid and Gibraltar, a mostly self-governing British overseas territory on Spain's southern tip that overlooks the only entrance to the Mediterranean Sea from the Atlantic Ocean. Spain ceded Gibraltar to Britain in 1713 under the Treaty of Utrecht but has long argued that it should be returned to Spanish sovereignty. Britain refuses to renounce sovereignty against the wishes of Gibraltarians. According to the British government statement, the Spanish Guardia Civil intercepted a local Gibraltarian sports fishing boat approximately 200 meters (yards) off the coast of Gibraltar. The two were transferred to Algeciras in Spain before being released.