MANILA - President Rodrigo Duterte committed an impeachable offense when he said Chinese fishers will not be barred from fishing in the Philippines' exclusive economic zone, his fierce critic Sen. Leila de Lima said.

In a dispatch from her detention cell, De Lima said Duterte’s pronouncements, deemed as policy statements, “are simply repugnant” to the Philippine Constitution as well as the United Nations Convention on the Law of the Sea and the South China Sea arbitration ruling favoring the Philippines.

De Lima added Duterte’s most recent statement “palpably shows a pattern of an open and brazen disregard of the rule of law and betrayal of the national interest.”

“We have here clear grounds for impeachment: culpable violation of the Constitution, treason and betrayal of public trust.”

De Lima, however, said with Duterte’s allies dominating the House of Representatives, where an impeachment complaint is initiated, it would be “wishful thinking” to expect the lower chamber to act seriously and favorably on the matter.

Duterte earlier this week was asked if the Philippines should bar China from fishing in the Philippines' exclusive economic zone, to which he replied that 2 countries are "friends" and that there should not be any "bloody conclusion."

• Duterte tells Pinoy fishermen in Reed Bank incident: 'I'm sorry but that's how it is'

His spokesperson Salvador Panelo later said the government would "tolerate" China's fishermen in the EEZ, where Manila has exclusive rights to resources, based on a 2016 ruling of a United Nations-backed court.

Under the constitution, all resources in the EEZ should only be for Filipinos, noted Jay Batongbacal, director of the University of the Philippines (UP) Institute for Maritime Affairs and Law of the Sea. The Fisheries Code, he added, deems the entry of foreign vessels into the 200-nautical-mile area as poaching, which can be fined.

Duterte views China as a friend on the basis of trade relations, said Panelo, who also serves as the President chief legal counsel.

The UNCLOS, Panelo added, allows the Philippines to grant another state privilege to fish in its EEZ.

Tensions between Manila and Beijing recently rose after a Chinese vessel rammed a Filipino fishing boat in Reed Bank (Recto Bank) last June 9.

Twenty-two Filipino fishermen were left at sea by the Chinese crew after sinking their boat. They were later rescued by a Vietnamese vessel. An investigation is underway to determine whether the ramming was intentional.

Duterte has downplayed the incident, prompting outrage from critics who want Manila to stand up to Chinese aggression.

Competing claims over the South China Sea are a point of regional contention because trillions of dollars of goods pass through it, and rich petroleum reserves are thought to sit deep beneath its waters.