Rajoy said Wednesday that the Catalan authorities lack the legitimacy to propose a unilateral declaration of independence.
"The illegal referendum that was held to undermine our democracy, Spanish unity and the Statute of Catalonia has failed miserably, and no outcome from that referendum can serve to legitimize Catalan independence," he told the parliament.
The prime minister also said that Spain will breakup only if all its citizens decide so.
"No European constitution recognizes the right to self-determination. The independence of Catalonia goes against all rules of international law," the Spanish prime minister said.
He added that the international mediation was unnecessary to ease tensions in the country.
The referendum was surrounded by scandal with the central government sending the national guard the region in an effort to disrupt the vote. The official results of the vote showed that 90.18 percent, or more than 2.28 million voters, supported the secession of Catalonia from Spain, with a turnout exceeding 43 percent. However, Madrid refused to recognize those results.