Recent reports in Spain have suggested that the Spanish centre-back and goalkeeper Iker Casillas have asked the club's board to sack Mourinho at the end of the season.
"A plot against Mourinho? It's just a big lie," Ramos told reporters. "We are all united at Madrid.
"In recent weeks the team has been on a very good run, and that accumulation of victories can only encourage us going into Wednesday's match [against Barcelona in Copa del Rey semi-final first-leg].
"It bothers me that I'm not able to play [because of suspension], but I have to comply with the sanctions."
Ramos scored in Madrid's 4-0 victory over Getafe at the Bernabeu in La Liga on Sunday.