Malacañang on Thursday challenged Vice-President Sara Duterte-Carpio’s camp to present evidence supporting its claim that an alleged plot dubbed “Oplan Romanov” existed, BusinessWorld reported. The demand came after Ms. Duterte’s camp cited the plot to justify her statement against President Ferdinand R. Marcos, Jr.

At a Palace briefing, Press Officer Clarissa A. Castro said it was up to Ms. Duterte’s team to prove the existence of the alleged operation. The Vice-President had earlier made remarks against the President, which her camp attributed to threats under “Oplan Romanov.” The Palace has repeatedly denied any such plot.

The development escalates the political tension between the two highest elected officials. Analysts say the lack of evidence could further strain relations, while the Vice-President’s camp has not yet issued a formal response to the Palace’s challenge.