"When I needed Jens most, he just walked away," Grethe Knudsen, who served as a minister in Labour governments from 1992 to 2001, told a press conference on Wednesday morning, justifying her decision to drop her 'book bomb' on the election campaign.
In the autobiography, titled 'Basketak', which translated roughly as 'The Scrap' or 'The Scuffle', she attacked Stoltenberg for being "evasive".
"When ministers want a conversation about difficult issues, it is not easy to get through to him," she wrote. "His eyes start to wander."
She accused Stoltenberg of deserting Thorbjorn Jagland, the Labour Prime Minister of the early 1990s, when he came under attack for his poor tactics in the 1997 election, and was branded "stupid" by party heavyweight Gro Harlem Brundtland. In the press conference Knudsen said she and Brundtland had never got on well together either.
The book has been widely condemned by her former colleagues, with Labour MP Martin Kolberg accusing her of harbouring "evil intentions".
"It is very disappointing that she concocts such hurtful and obnoxious comments about people she has worked with," said her former ministerial colleague Thorbjørn Berntsen. "She could at least have waited until after the election."
But Knudsen defended the timing of her book, arguing that "it's now, during the election campaign, that politics are on the daily agenda".
She said that she didn't expect the publication would not damage Labour's chances.
"This will blow over. Next week there will be new issues," she said. "It is appropriate for me to write now, after I've been through a period of severe disease, with cancer and a stroke."