Derry came under fire from his parent club this week after apparently snubbing a plea from his boss Dennis Wise to return to Elland Road as midfield cover.
Leeds' assistant boss Dave Bassett said Wise felt 'angry and disappointed' about the decision.
However, Warnock says it was not the player's decision to make and that it was he as Palace boss who ensured the player would see out his loan deal until January 19.
"Dennis asked me on New Year's Eve for permission to let Shaun go back to Leeds before January 19, but I refused because I have to look after the interests of my own club," Warnock told the Yorkshire Post.
"The loan deal runs until January 19 and I have told Shaun 'I am sorry, but I cannot let you go back before then'. We need him here.
"Shaun knows he is a Leeds United player, but the decision was not his to make. It was mine as the manager of Crystal Palace."