Relations between powerful vice president and president continue to deteriorate, as investigators summon Duterte.

Philippines Vice President Sara Duterte has insisted that she has not schemed to kill the president, as investigators summoned her to testify.

Duterte told reporters on Tuesday that her instruction to have her estranged ally President Ferdinand Marcos Jr killed was a “plan without flesh”. The statement came shortly after investigators said they had summoned the official to appear before them.

Duterte told a briefing at the weekend that she had ordered someone to kill Marcos, along with his wife and cousin – the parliament speaker – if any potential plot to assassinate her should be successful.

Duterte sought to emphasise to reporters that the main condition of her plan was that she be killed first.

“My question now to the administration: Is revenge from the grave a crime?” she asked, saying that she only made the comments out of “consternation” with the president.

The daughter of former President Rodrigo Duterte criticised the Marcos administration’s “failure to serve the Filipinos while it masterfully persecutes political enemies”.

“Common sense should be enough for us to understand and accept that a supposed conditional act of revenge does not constitute an active threat. This is a plan without flesh,” Duterte said.

The country’s justice department on Monday called the vice president the “self-confessed mastermind” of a plot to assassinate the president and issued a subpoena demanding her appearance at a formal inquiry.

The president also promised to act against what he described as a “troubling” public threat against him.

“Such criminal plans should not be overlooked,” he stated.

The dispute comes ahead of general elections in May.

Marcos and Duterte achieved a landslide victory in the Philippines’ 2022 elections after banding together as running mates, but their powerful families have clashed since.

Duterte stepped down as education secretary in June, later saying she felt “used” after teaming with Marcos. She remains the president’s constitutional successor in case he is unable to complete his six-year term.

Both families have accused one other of drug abuse, although neither has provided evidence.

An investigation is continuing over Duterte’s alleged misuse of millions of dollars worth of government funds.

The International Criminal Court, meanwhile, is running an investigation into potential crimes against humanity against the vice president’s father, Rodrigo Duterte, who operated a deadly war on drugs during his time as president.

Marcos has repeatedly ordered his government not to cooperate with investigators from the top United Nations court after the Philippines withdrew its membership.