MANILA (UPDATE)—Malacañang on Friday said former Foreign Affairs Secretary Albert del Rosario may have "misused" his diplomatic passport for his Hong Kong trip.

Presidential Spokesman Salvador Panelo raised the possibility given that the former top diplomat's trip was not sanctioned by the Philippine government.

"Mr. Del Rosario may have misused a diplomatic passport in his travel to Hong Kong, a trip which is private in nature and is in no way related to government or foreign service," Panelo said in a statement.

"As the country's former Chief Diplomat, Mr. Del Rosario should have known or have been alerted to the proper use of diplomatic passports and other travel documents."

Palace says former DFA Sec. Albert Del Rosario may have “misused” a diplomatic passport for his Hong Kong trip. @ABSCBNNews pic.twitter.com/dKYl8uOg0R

— Arianne Merez (@arianne_merez) June 21, 2019

Del Rosario, who bears a diplomatic passport, was not allowed to stay at the Chinese administrative region after nearly 6 hours of questioning by immigration officials on Friday.

• Hong Kong denies entry to Philippines' former top diplomat

A non-executive director of Hong Kong's First Pacific, Del Rosario went to Hong Kong to attend a shareholders meeting.

Philippine Consul General in Hong Kong Antonio Morales said immigration authorities did not give a clear reason or "elucidation" on why Del Rosario was denied entry.

He said the Philippine consulate was just given "immigration regulations" for an explanation.

Upon his return to Manila on Friday afternoon, Del Rosario decried the incident as a violation of the Vienna Convention on Diplomatic Relations.

• Ex-top diplomat Del Rosario back in Manila after Hong Kong deportation

"I think clearly the bottom line is I was being harassed or we were being harassed. And I think the reason might be, if you follow the trend, the honorable Ombudswoman who’s here, she went through the same experience. And the link to that experience, which turned out to be consequential to us, was the ICC communique," he said.

Article 40 of the convention provides that a diplomatic agent is entitled to "inviolability and such other immunities as may be required to ensure his transit or return" through a territory of a third state.

Del Rosario said the Foreign Affairs department has suggested to him to consider filing a protest against Hong Kong.

He added that he has never encountered a problem in using his diplomatic passport prior to filing the communication against Chinese President Xi Jinping.

"As I said earlier, I sit on the board of First Pacific and it calls for visiting Hong Kong for meetings, regularly, 4 to 5 times a year. And each of those the diplomatic passport is a privilege given to former SFAs (Secretary of Foreign Affairs). So I’ve taken advantage of that," he said.

"Never [had problems before], not even a hint of a problem."

The Palace, however, highlighted that "any country has the authority and the right to bar entry to any foreign national to its territory."

Last month, former Ombudsman Conchita Carpio Morales experienced the same ordeal when she flew to Hong Kong for a family vacation.

Morales, who along with Del Rosario and a group of Filipino fishermen hauled the Chinese leader to the International Criminal Court for alleged crimes against humanity, was also held for questioning at Hong Kong Airport.

Following Morales' experience, Panelo said Del Rosario "should have been prudent enough to ensure that Hong Kong, a Chinese Special Administrative Region, has no objection to his entry."

• Del Rosario should have learned from Morales' HK trip: DOJ chief

Panelo meanwhile assured Del Rosario that the Philippine government would continue to help him "notwithstanding his penchant to capitalize and politicize issues" related to President Rodrigo Duterte's foreign policy towards China.

"He remains a Filipino citizen entitled to protection and assistance from the Philippine Government," Panelo said.

Del Rosario is a vocal critic of the Duterte administration's friendlier stance towards China despite the maritime dispute.

• Palace asks Del Rosario: Why go to Hong Kong?