A volunteer hands out leaflets of Jimmie Åkesson's Sweden Democrats ahead of the election in 2014 | Jonatan Nackstrand/AFP via Getty Images Swedish far right at record high in pre-election poll The ruling center left struggles to respond to rhetoric on crime and immigration.

Support for the far-right Sweden Democrats is at a record high ahead of September's election, putting them hot on the heels of the ruling Social Democrats and main opposition Moderates, according to a new poll.

The anti-immigrant party scored 20 percent in the Ipsos poll in Dagens Nyheter, just four points behind the Social Democrats and two points behind the center-right Moderates.

Dagens Nyheter said Prime Minister Stefan Löfven's Social Democrats have never polled so low in May of an election year since its Ipsos series began in 1979.

The Social Democrats, who have dominated Swedish politics for a century (but were in opposition from 2006-2014), have struggled to respond to the far-right party's tough rhetoric on crime and immigration, needing to strike a balance between reassuring the population and sticking to their traditional values.

The Sweden Democrats, led by Jimmie Åkesson, appear to be on track for their strongest result so far in the vote on September 9. After entering the Riksdag (parliament) in 2010, they scored 13 percent in 2014's election.

Voter intentions for Löfven's party have fallen from 29 percent in a February poll, the paper said. The Social Democrats won 31 percent in 2014, when they formed a minority coalition with the Greens, with parliamentary support from the Left Party.