According to the paper, Sandberg, who announced this week he was stepping down as deputy leader, thrust the other politician against a wall while shouting angrily at him.
The attack was reportedly so serious that Sandberg had to be physically separated from the other politician, and the party was forced to launch an internal inquiry into what had happened.
Sandberg's wife, Line Miriam Sandberg, who serves as county leader for the party in Troms, is thought to be central to the dispute, the paper reported, adding that it had been bubbling on for years in the Troms party organisation.
In a Facebook post yesterday, Line Sandberg said that her husband's enemies in the party would try to discredit him in the run up to the publication of his memoir, 'Against my will - Clearing up a political life', which is released next month.
"Some will in the future, for fear of the book, do everything they can to discredit Per and me, well aware that we will not say anything until the book comes out," she wrote.
According to VG, Per Sandberg has been emailing some of his colleagues warning them of the book's contents, and giving them one last chance to respond.
“If people have anything to fear then they surely have something to fear,” Sandberg told NRK, somewhat cryptically, on Tuesday, although he denied that the book had anything to do with his resignation.
He also hinted that his decision to step down from frontline politics for the moment did not spell the end of his political career.
"Let me put it this way, everyone who has predicted my political death will get a surprise," he said.