The latest EU-poll, carried out by Sentio for newspapers Nationen, Klassekampen, and Dagen, found only a 3.8 percent point difference separating the two camps, a smaller margin than during the previous vote for membership in 1994.
The latest polls showed 46.8 percent against EU membership and 43 percent in favor.
"I interpret this survey as expressing that we on the 'no' side must taken nothing for granted," Heming Olaussen, leder of "Nei til EU" (No to EU) told Nationen.
The poll has inspired the group to step up their efforts.
"If this trend continues it opens the way for a new EU debate in Norway, and we will be ready for that," Olaussen said.
Grete Berget, secretary general of Europabevegelsen (Europe Movement) does not believe the result is linked to any particular event.
"There have been no major events in recent months that would indicate a shift to the 'yes' side," Berget said.
