The three party opposition of the Social Democrats, Green party and Left party mustered 57.6 percent of the vote in the February poll in comparison to 38.2 percent for the Alliance government.
The gap between the two blocks has increased by 5.7 percentage points since December.
The Social Democrats gained 45.5 percent in the February poll, up 2.4 percentage points since December and the party’s highest standing since 1994.
Fredrik Reinfeldt’s Moderates stand at 21.4 percent, up 1 point since December.
The Green party and the Liberal party (Folkpartiet) both gained 6.6 percent after falling 0.6 and 0.8 percentage points respectively. The Centre party declined by 0.8 percentage points to 6.0 and the Left party by 0.5 points to 5.5. The Christian Democrats fell 1.1 percentage points to 4.2.
The far-right Sweden Democrats remained unchanged at 2.9 percent.
The poll was conducted by Sifo and is based on interviews with 1,905 people conducted between the 4th-14th of February. The changes in voter support are not statistically significant.