The Social Democrats, Green Party and Left parties together polled 48.6 percent to the Alliance parties’ 42.2 percent in the Sifo poll, published in the Svenska Dagbladet daily on Sunday.
The Sweden Democrats meanwhile came in at a record 7.7 percent, up 0.5 percentage points on the previous poll.
The Green Party are behind the opposition bloc’s climb, up 1.1 points on the previous month’s poll. The Social Democrats meanwhile declined 1.2 points.
The Moderates climbed marginally by 0.1 points to 28.8 percent.
The Liberal Party (Folkpartiet) was down 1 point, the Centre Party down 0.4 points and the Christian Democrats dropped further below the 4 percent threshold for parliamentary seats.
Göran Hägglund’s Christian Democrats polled 3.4 percentage points, down 0.4 points on the previous poll.
At about the halfway point in the Swedish parliamentary term, it remains unclear however whether the Red-Greens are ready and able to form a coalition in time for the election in 2014.
The Sweden Democrats have enjoyed fairly stable support since the 2012 election and the latest poll indicated that the party will retain its balance of power status in the Swedish parliament after 2014.
The party on Friday announced a “clean out” of its rank and file with party leader Jimmie Åkesson declaring that he was eager to curb the stream of racist and homophobic comments made by party members since the 2010 election.