"Remarks allegedly made by the programme's producers that the show had survived after Whiteley's death in 2005 and would continue without Vorderman, were "below the belt" and "crass", Ms Apanowicz said.
"That upset me deeply as his partner, and it did upset Carol deeply, and it's upset all of Richard's friends.
"It's nasty. You don't need to say things like that."
Mr Stellman, who devised and owns the rights to the Countdown format worldwide, said he had told producers he was "upset" about "the way Carol was treated after 26 years of loyalty and devotion".
"I think they could've done something, shall we say, simply and human by saying, 'Carol, we love you dearly. You did a wonderful job for all those years. We're terribly sorry to lose you. Unfortunately it seems to be something that we can't afford.'"
"I'm sad that it happened," he told the BBC News website.
"It could've been done in such a lovely way, with great dignity, but I'm afraid some people who deal with things sometimes forget what that means."
However Mr Stellman stopped short of saying he would withhold the rights to the programme in future, insisting he was "misquoted" in a Daily Mirror report suggesting this.
"I don't want to feel that I have any truck with anybody who does anything because I'm only responsible for the format rights," he said.
Des O'Connor (left) has announced he will quit Countdown in November
"My format rights are covered and if they respect them, which they don't always do obviously, I will respect them."
Vorderman was part of the original team on the words-and-numbers game show.
It was the first programme to be broadcast when Channel 4 began in 1982.
She started as the maths "expert" who would check contestants' sums in the numbers rounds, but took on extra duties to become a sidekick to Whiteley.
Last week Countdown's current host, Des O'Connor, announced he would leave the show in November after presenting more than 500 editions.
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