The crime drama will come to an end after its ninth series but Johnston told TV Times that the decision made her feel "robbed".
"I'm very sad about it," she said. "It was a lovely job. The show gets great audiences, it's sold all over the world and I don't quite get why it's going."
Johnston added that the show may have been dropped for financial reasons, saying: "They say it's too expensive to make in these austere days."
Meanwhile, Eve claimed that the show had an "audience appreciation rating of 90%" but added that he would rather it was cancelled than made on a tighter budget.
"They could make it if we changed how it's done at the moment, but I don't want that," he said. "I can't see the point of suddenly delivering a show that's a different kind of programme, just to cut costs. The BBC can go and make other stuff that costs them less money, that's fine."
However, the BBC's controller of drama commissioning Ben Stephenson defended the move, saying: "It's always hard bringing successful series to a close, but like Ashes To Ashes and Mistresses, we want to end on a high."
Waking the Dead returns for its final series on Sunday, March 13 at 9pm on BBC One.
> BBC announces Waking the Dead spinoff