Metro Manila (CNN Philippines, October 16) — Trust and satisfaction surveys might be part of a plot to destabilize the President, former senator Bongbong Marcos said on Monday.

Speaking to CNN Philippines' The Source, the former vice presidential candidate said approval ratings might be meant to turn public opinion against President Rodrigo Duterte.

"This is a way of making the mindset to say that maybe we should destabilize Duterte because he's not popular anyway," Marcos said.

"It's very clear that there are groups that are working very hard to destabilize Duterte's government. Now, I don't know, maybe this (the survey) is part of it. But this is all speculation," he added.

President Rodrigo Duterte's ratings dropped in the most recent Social Weather Stations (SWS) survey, even as he maintained high approval and trust scores with another pollster, Pulse Asia.

SWS has no comment on Marcos' speculation. However, it previously said that such a drop is "a normal phenomenon for all past presidents."

Related: Drop in Duterte's satisfaction, trust rating normal - SWS

Critics of the President said the decline in ratings showed dissatisfaction with the war on drugs and failure to deliver on promises, such as solutions to traffic, stopping 'endo' (end of contract) employment.

Marcos added that while he believes in hard data, there are many ways to interpret them.

"The art is in the interpretation… I don't know that those who are doing the interpreting right are very objective," he said.

Related: The science of rating a Philippine public official

The former senator also commented on Duterte's threat to declare a revolutionary government in response to supposed destabilization efforts.

"It is certainly a radical move, but I think the efforts to destabilize him have already been very clearly shown… There are very large, great forces that are working hand with each other to try and unseat him," said Marcos.

Duterte on Saturday said he would declare a revolutionary government and "full-scale" war with the New People's Army if the alleged plot against him went out of hand.

Related: Duterte warns of revolutionary gov't if destabilization plots escalate

Marcos has a pending protest at the Presidential Electoral Tribunal against Vice President Leni Robredo.