MANILA - The filing of the first impeachment complaint against President Rodrigo Duterte is "plain and simple stupidity," House Speaker Pantaleon Alvarez said Thursday.

"We are all entitled to our own stupidity... That is stupidity, we know that all the charges are fabricated. They seem to believe their own lies," Alvarez said in a phone interview with ABS-CBN News Channel.

Magdalo Rep. Gary Alejano lodged the impeachment complaint against Duterte in connection to the killings in his war on drugs and allegations he kept secret bank accounts.

The President, Alejano alleged, was culpable of violation of the Constitution, betrayal of public trust, graft and corruption, bribery and other high crimes.

Alvarez swatted aside the allegations, saying these were not only unsubstantiated but had also placed the proof of burden on the President.

"When you allege something, you have to prove it, that's the rule. You cannot accuse me of anything and shift the burden of proof on my part. That is pure and simple stupidity," he said.

Alvarez said he was "very, very confident" that the impeachment bid will not prosper in the lower house, which is dominated by the President's allies.

The House leadership needs to transmit the complaint before the justice committee, which will determine if it is sufficient in form and substance.

If approved by the House, the complaint will be heard by the Senate, which will convene as an impeachment court. A two-thirds vote of the Senate tribunal is needed to impeach an official.