Over the past week, the rating of the CDU/CSU alliance fell one percentage point to 29 percent, its lowest level since 2006, according to the poll published in the Bild am Sonntag newspaper.
The survey's results demonstrated that the support for the German Social Democratic Party (SPD) also dropped by 1 percentage point to 18 percent, the Alternative for Germany (AfD) party's rating remained at 15 percent, while the Green Party's rating increased to 14 percent from 12 percent a week earlier.
Die Linke and the Free Democratic Party (FDP) maintained their positions, with public support at 10 percent and 9 percent, respectively.
The poll was conducted from July 19-25 among 2,001 German citizens.
The coalition crisis between the CDU and the CSU on the migration issue has been ongoing. In early July, the parties agreed to take measures to curb illegal migration to Germany.
The deal included, among other things, boosting control along the border to prevent illegal migrants from entering the country, as well as the creation of transit centers in Germany, where migrants will stay up to two days before deportation to other EU countries where they were originally registered.