Reform Party founder Preston Manning broke his long silence on Sunday and finally voiced his opinion of Stockwell Day, saying he lacked judgment and bungled the leadership.

Manning told CTV's Question Period that his successor as Canadian Alliance leader didn't always tell the truth.

"All of us make errors in judgment but I think that was compounded then with the way that it was explained -- communication of those errors in judgment crossed the line where a lot of what was said simply wasn't really true," Manning said.

"I think that's what lost Stock the confidence of some of the very key people in the Alliance caucus," he said. "The lesson in that is . . . somehow we got to learn to tell the truth even when it hurts."

Manning ended his self-imposed silence just as his new book readies to hit store shelves, entitled Think Big: My Adventures in Life and Democracy.

The book says Day bungled the leadership through poor judgment, playing with the truth, refusing to heed advice, mixing politics with religion and communicating poorly.

But not everyone appears to be behind Manning in his assessment of Day's abilities.

Alliance MP Peter Goldring accused Manning's comments of being the sour grapes of a man bitter over losing the party leadership.

Calgary Southeast MP Jason Kenney, who co-chaired Day's failed leadership campaign against the party's current leader Stephen Harper, said Manning is just sore.

"I feel sorry for Mr. Manning," Kenney told an Edmonton newspaper. "His greatest mark was as a champion of democracy and he hasn't gotten over a democratic decision made by our party years ago. The rest of us have moved on."

Calgary Northeast MP Art Hanger said he isn't condemning Manning for speaking out.

"There's often a viewpoint offered by a political figure to analyze things from his perspective," Hanger said.