Rams boss Billy Davies has asked about King's availability in recent days, but knows there's no chance of the forward leaving Vicarage Road this summer.
"As long as I am here, he is here. He will stay. All these reports are just speculation."
King's opinion of his manager's stance remains to be heard.
The 27-year-old has made no secret of his desire to return to the top division, but now appears to face at least one more year in the Coca-Cola Championship.
Boothroyd continued: "Is Marlon happy? I would think so. He was when I saw him last.
"He stays. He is part of the core of the team who won promotion (in 2006).
"He missed out last year in the Premiership, but he is going to get us back there.
"He is a key part of my plans, so a move isn't going to happen. He is staying."