MANILA - President Rodrigo Duterte cannot heed the request of lawyer Larry Gadon to be a special prosecutor in the impeachment proceedings against the Chief Justice Ma. Lourdes Sereno, the president's top legal counsel said.

Chief Presidential Legal Counsel Salvador Panelo said it would be unconstitutional for Duterte to accept Gadon's request as the President is not allowed to hold any other office.

"You cannot do that because constitutionally, the President cannot hold any office outside of being president," Panelo told ANC Early Edition Monday.

• Duterte cannot prosecute Chief Justice: Sereno camp

Panelo believes Gadon is just complimenting Duterte, who was a prosecutor before he became mayor of Davao City, and eventually president of the country.

Last Saturday, Gadon said he plans to ask Congress to authorize Duterte as a special prosecutor in the impeachment proceedings of Sereno

His complaint was already declared sufficient in grounds by the House justice committee, voting 25-2, last Thursday. The complaint stemmed from several accusations, including Sereno's alleged non-disclosure of the fees she got from the Piatco case in her 2010 SALN.