The approval rating for the conservative main opposition People Power Party (PPP) has topped 40 percent in Seoul, expanding its lead over the liberal ruling Democratic Party (DP) in the runup to next week's Seoul mayoral by-election, an opinion poll showed Monday.

According to the Realmeter survey conducted on 2,516 voters nationwide from last Monday through Friday, the approval rating for the PPP came to 41.2 percent, up 2.3 percentage points from a week ago.

This marks the first approval rating of over the 40 percent threshold for the PPP in Seoul in Realmeter surveys after the conservative party first overtook the DP in the survey in the first week of March, with a 34.2 percent approval rating.

The PPP then saw its rating rise further to 36.4 percent and 38.9 percent in the following weeks, the poll results showed.

The approval rating for the DP, meanwhile, came down to 25.6 percent in the latest opinion poll, down 0.6 percentage point from a week earlier.

The latest survey results came ahead of the mayoral by-elections set for April 7 in Seoul, as well as Busan, the second-biggest city.

Currently, PPP Seoul mayoral candidate Oh Se-hoon is leading DP rival Park Young-sun by a margin of around 20 percentage points in various opinion polls. In Busan, PPP candidate Park Hyung-jun is also leading DP rival Kim Young-choon by a solid margin.

The latest Realmeter poll also showed that the approval rating for the PPP in the southeastern region encompassing the cities of Busan and Ulsan and South Gyeongsang Province also rose by 0.1 percentage point to 42.1 percent.

The corresponding rate for the DP was 24.4 percent, up 0.9 percentage point from a week earlier.

Nationwide, the combined approval rating for the PPP rose by 3.5 percentage points to 39 percent, while the DP saw its rating inch up by 0.2 percentage point to 28.3 percent.

The countrywide rating for the PPP marks its highest since the 36.3 percent it recorded in the second week of August last year.

The poll put the approval rating for President Moon Jae-in at 34.4 percent, up 0.3 percentage point from a week earlier. The disapproval rating inched up by 0.3 percentage point to 62.5 percent, the highest reading ever for Realmeter polls.

The survey, commissioned by cable news channel YTN, has a 95 percent confidence level, with a margin of error of plus or minus 2 percentage points. (Yonhap)