Rafael Benitez was appointed on a short-term deal in November to replace sacked Champions League-winning boss Roberto Di Matteo but was never popular with fans and results have not improved.
He said: "I have been in charge in football for 26 years. I have won the Champions League, won the FIFA Club World Cup, the FA Cup, the Italian Supper Cup, the Spanish league twice, nine trophies, all the trophies you can win at club level.
"A group of fans, they are not doing any favours for the team when they are singing and wasting time preparing banners.
"It's because someone made a mistake. They put my title (as) 'interim manager', and I will leave at the end of the season, so they don't need to waste time with me.
"They have to concentrate on supporting the team, that's what they have to do.
In the end, they are not doing any favours to the club, to the rest of the fans and to the players.
"Every game they continue singing and they continue preparing banners, they are wasting time. What they have to do is support the team.
"If we cannot achieve what we expect to achieve, that is to be in the top four and be in the Champions League for next year, I will leave; they will stay in the Europa League."