Metro Manila (CNN Philippines) — Davao City Mayor Rodrigo Duterte has maintained his lead over other presidential candidates in the latest Social Weather Stations (SWS) survey conducted April 18-20.

The results of the survey, first published on Businessworld on Sunday (April 24), show that one in three respondents (33 percent) chose Duterte as president.

When the survey was conducted, Duterte was facing criticism over his rape remark about an Australian missionary killed during a 1989 hostage taking in Davao City. Nevertheless, the mayor saw his support grow 6 percentage points from 27 percent in the previous March 30 to April 2 survey by the SWS. The poll has a + 2 margin of error.

Independent candidate Sen. Grace Poe stood at second place (24 percent). Liberal Party bet and former Interior Secretary Manuel "Mar" Roxas II (19 percent) grabbed third place from Vice President Jejomar Binay (14 percent). They respectively scored 18 percent and 20 percent in the previous survey.

Sen. Miriam Defensor-Santiago was supported by 2 percent of respondents.

The SWS results are similar to the April 12-17 survey of Pulse Asia, showing Duterte drawing support from 34 percent of voters.

Robredo rises 7 points, ties with Marcos

In the vice presidential race, the SWS survey showed Liberal Party bet and Camarines Sur Rep. Leni Robredo inching past Sen. Ferdinand "Bongbong" Marcos Jr.

Robredo jumped 7 percentage points from the previous survey to take slightly more than a quarter (26 percent) of respondents. Similarly, one in four respondents (25 percent) chose Marcos as their vice president. Given the poll's error margin, both candidates are statistically tied.

Sen. Francis "Chiz" Escudero took the third spot (18 percent), followed by Sen. Alan Peter Cayetano (16 percent).

They are followed by peers Antonio Trillanes IV (5 percent) and Gregorio "Gringo" Honasan (2 percent).

During the March 30-April 2 survey, Marcos led candidates with 26 percent, followed by Escudero (21 percent) and Robredo (19 percent).

According to SWS, 1,800 validated voters from around the country took part in the face-to-face survey.