STOCKHOLM (Reuters) - Swedish prosecutors opened an investigation into alleged sexual harassment by the Sweden Democrats’ top candidate for the European Parliament election, throwing an unwelcome spotlight on the far-right party four days before the ballot.

Peter Lundgren, who is seeking re-election to the EU legislature, has admitted behaving improperly toward party colleague Sara-Lena Bjalko, blaming alcohol.

The prosecution authority said on Wednesday it had started a preliminary investigation into the incident.

Lundgren, who has neither resigned nor been disciplined by the party, could not immediately be reached for comment. A spokesman for the Sweden Democrats could not immediately give a comment.

In a video the party posted on YouTube this week, Lundgren said he had behaved rudely and apologized to Bjalko for the incident, which took place more than a year ago at a party.

Bjalko said she had put it behind her. “I have no intention of making a police complaint,” she said in the video.

In Sweden, members of the public can make complaints to the police in regard to certain crimes. Police declined to say who had filed the complaint against Lundgren.

The Sweden Democrats have blamed a rise in the number of sexual attacks reported to police in Sweden in recent years on increased immigration. Its leader Jimmie Akesson this month called the problem to a large extent “imported”.

The party, which also promotes anti-immigrant views, is tipped to get around 17 percent in the election, according to a Kantar Sifo poll published on May 10. That puts it second behind the center-left Social Democrats, on 23 percent.