"According to the text and meaning of the Constitution, as president of the Senate, I immediately assume the Presidency of the State envisaged by the constitutional order and I promise to take all the necessary measures to bring peace to the country," she said on November 12.
The Constitutional Tribunal, Bolivia's Sucre-based national court, confirmed the legitimacy of Añez becoming the president on Tuesday evening.
Añez's assumption of the presidency comes unilaterally, shortly after Bolivian lawmakers revealed they lacked quorum to formally approve Morales' resignation due to an inadequate showing from members of the Movemiento al Socialismo (MAS). Despite her declaration, a lack of a formal vote violates the Bolivian Constitution.
The interim leader stated that presidential elections will take place in Bolivia following the formation of a new election commission. A previous estimate from Añez claimed a new election will take place by January 22.
The lawmaker's new position follows the expedient resignations of Vice President Álvaro García Linera, Minister of Defense Javier Savaleta, the heads of both chambers of Congress and the head of the electoral commission - all of whom belong to Morales' MAS party.
Bolivian Foreign Minister Diego Pary announced his resignation shortly following Añez's assumption of power.
Earlier this week, dozens of staffers with the regional election commission were arrested in relation to an ongoing investigation concerning the results of the October 20 election.
Meanwhile, Brazilian Foreign Ministry said that the authorities of Brazil, the largest country in Latin America, recognize Bolivian opposition senator Jeanine Anez as the acting president of Bolivia.
Morales, who has fled the country for political asylum in Mexico, has said the recent series of events is part of a coup led by right-wing opposition leaders Carlos Mesa and Luis Fernando Camacho.
The ousted leader later denounced Añez's self-declared presidency as a blatant disregard for and violation of the Bolivian Constitution.
"The most artful and disastrous blow in history has been consummated. A coupist right-wing senator calls herself president of the senate and then interim president of Bolivia without a legislative quorum, surrounded by a group of accomplices and led by the armed forces and the police that repress the people," Morales said in a translated social media post.