A bid from Newcastle for Lyon midfielder Grenier has remained on the table as the Magpies pursue a replacement for Yohan Cabaye, who joined Paris St Germain this week.
But agent Frederic Guerra has announced Grenier will stay with his French club.
He told French sport website Le 10 Sport: "It's not easy to say no to a big club like Newcastle, but with Clement we have finally decided to stay at Lyon.
"Six months out from the World Cup, is a hasty departure just days before the end of the transfer market a good option? It's not a certainty. Lyon are starting to find their true colours and Clement didn't want to leave the club during the season.
"The conditions of his departure weren't creating a favourable context for his development. Clement would be arriving at Newcastle not as Clement Grenier but as a replacement for Yohan Cabaye.
"I have the greatest respect for the quality of player that Cabaye is, deserving of everything that is said about him. However, as Clement Grenier's agent I am obliged to say: is Clement worth just half what Yohan Cabaye is?
"Above all the reasons which have led us to decline the offer from Newcastle, the conditions of the deal didn't seem fair to Clement."
If Grenier and his agent cannot be persuaded to reconsider, Newcastle manager Alan Pardew may have to cope without his main midfield target.
As it became obvious that Cabaye would get his move to Paris earlier this week, Pardew turned his attention to finding a suitable replacement.
Asked on Thursday if he was hopeful of landing Grenier, Pardew said he was "obviously hopeful".
Asked further if his hand would be weakened should no replacement arrive, he added: "Well, of course. You can't take a player out like Cabaye and say it's not going to weaken you. It is, unless we can replace him like for like.
"But whether we can do that, I don't know."
Pardew has at least brought in a striker this week, and he has challenged new recruit Luuk de Jong to make himself an instant hero on Tyneside.
The 23-year-old striker completed a loan move for the rest of the season to St James' Park on Wednesday, and will go straight into the squad for the derby against Sunderland on Saturday.
De Jong has not started a game for Borussia Monchengladbach this season and his last goal for the club came in April, but Pardew has told him to be ready to make a swift impact.
The 52-year-old said: "I said to him, 'You could become an instant hero if you play or you get on the pitch in terms of a substitute's appearance'.
"That must be his immediate dream. It certainly would be mine if I was a striker."
De Jong's arrival in the north-east came some 18 months after the Magpies first tried to sign him, and Pardew is hoping it will be worth the wait after his spell in the Bundesliga proved a difficult one.
He said: "I'm pleased in so much that he's a player we have had our eye on for a while.
"He was someone we couldn't quite reach in his last transfer move in terms of the finance, but that hasn't worked out as perfectly as perhaps they both hoped, the team and Luuk, and he's ended up here.
"But he has done well today and we are looking forward to his inclusion in the squad. He's a big presence of a player, he's a goalscorer and if there's a criticism you would aim at us, maybe we could do with scoring a few more goals."
The Holland Under-21 international has already signalled his readiness to start the derby if required, but Pardew has hinted that that is unlikely despite his relative lack of options.
He said: "Well, he hasn't had much game action and this is the Premier League, so I would suggest that I might be a better judge than he is.
"But I like his confidence and he has trained very well today, so I am very pleased with him."
French striker Loic Remy is certain to sit out the derby after failing in a bid to have his sending-off at Norwich overturned.
The Magpies lodged an appeal against the 27-year-old's dismissal along with Canaries midfielder Bradley Johnson after the pair clashed late in Tuesday night's 0-0 Barclays Premier League draw at Carrow Road.
However, while Johnson's own effort to clear his name was successful, Remy's hopes were dashed and he will miss the league games against Sunderland, Chelsea and Tottenham.
A Football Association statement said: "The claim involving Newcastle's Loic Remy was dismissed, therefore his three-match suspension remains with immediate effect."