Harry Redknapp is in talks to take over at Loftus Road after the Welshman, who replaced the now-Leeds boss in January.
"I would like to wish Harry Redknapp the best of luck filling my old seat in the dugout at Queens Park Rangers," Warnock wrote in The Independent.
"It was one of the achievements of my managerial career getting QPR back into the Premier League after a 15-year absence and I would be very sad to see them go back down after all the hard work the players, staff and myself put in.
"Neither the fans nor the owners, Tony Fernandes and Amit Bhatia, deserve that."
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"It was difficult to accept when I was replaced," he added. "Having met the mandate of keeping out of the bottom three we were about to make the signings in the January window we needed to head towards mid-table.
"Having kept QPR up, I planned to retire and hand the reins over to someone else for a smooth transition. It is easy to look back in hindsight but I think Tony might now reflect and feel that would have been a better way to proceed."
Despite QPR being winless at the bottom of the Premier League, the Leeds manager feels that Hughes' side were sometimes given too much credit.
"I have to admit there have been times this year when I have had to bite my tongue," Warnock noted. "I kept hearing the team were playing well without getting the results they deserved; so were mine but we did win away from home three times.
"There was also the comment at the end of last season when my successor said after coming 17th - the same position I left them in - 'we won't be in this position again'. Unfortunately he was proved right; QPR have not been that high since."