MANILA - Vice President Robredo on Monday submitted a letter to Malacanang stating her resignation from the Duterte Cabinet.

In a Twitter post, Robredo's office said the letter was received by the Office of the Executive Secretary past 9 a.m.

Robredo wrote that Duterte's order for her to "desist from attending all Cabinet meetings" has "made it impossible for me to do my job."

Robredo first announced her resignation from the Cabinet late Sunday, citing "major differences" with Duterte and suspicions that a plot was underway to unseat her from the number two job.

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Robredo said she had clashed with Duterte over his policies, including his war on drugs, which has killed over 2,000 people in the past five months, and his push to reinstate the death penalty.

She has not been shy about criticizing him, including over his "improper" public remarks about her appearance and private life.

Robredo, 52, a former lawyer and social activist, said she joined the Cabinet because she believed helping the poor was one thing she and Duterte could agree on.

"From the very beginning, the president and I had major differences in principles and values," she added.

Robredo came from the party of previous president, Benigno Aquino. She defeated by a narrow margin Ferdinand Marcos Jr, the son and namesake of the late dictator overthrown in a 1986 revolt.

Her election in May was dogged by allegations by Marcos Jr that the vote count was rigged to ensure the Robredo's Liberal Party had a stake in Duterte's executive.

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Robredo was especially critical of last month's burial of his father at a "heroes' cemetery", saying it was an insult to the memory of those who suffered under the martial law Marcos imposed in 1972, in what was one of the darkest chapters of Philippine history.

Duterte supported the burial of Marcos, who was widely accused of brutality and plunder and enriching his cronies and family, which remains influential in politics. -- With a report from Reuters