Earlier in the day, all factions of Spain’s lower house of parliament agreed that Spain should not support the bloc’s agreement with Turkey.
"This agreement, if supported by Spain, could form a basis for serious human rights violations and non-compliance by Spain with its international obligations…The EU will violate some basic principles of international law if it approves the agreement proposed by Turkey," the group's statement said.
Protests against the current EU refugee agreement with Turkey are expected to be held across dozens of Spanish cities later on Wednesday.
Earlier in March, Ankara pledged to take back all undocumented migrants that had arrived to the European Union and send in their place documented Syrian refugees on one-for-one basis in exchange for a total of 6 billion euros ($6.6 billion), the acceleration of visa liberalization negotiations and EU accession talks.