The Flicker singer made the shock revelation after seeing the TV funny-man share a video about the upcoming BRIT Awards, which he is hosting.
In the clip, Jack hilarious can be seen mocking his presenting skills and calling out his faux-pas from last year’s show.
Listing a round-up of celebs he offended during the 2018 show, which included Sam Smith, Ed Sheeran and England football legend Harry Kane, Jack said: “I would like to say sorry to Niall Horan.”
Putting on a faux Irish accent, Jack mockingly continued: “Hello Niall.
“I am sorry little Niall… I love you really.”
Looking off camera the star added: “Did I patronise him again?”
Putting on a straight face, Gemma Chan’s ex said: “I am sorry to all of you and I promise that in 2019 I will not harm any celebrities.
“Any way I will see you all on February 20 for the BRITs on ITV.”
Pretending he was unimpressed, Niall tweeted Jack: “We’re not mates anymore.”
This year the official BRITs red carpet will be streamed live on Facebook.
Hosted by Made In Chelsea star Jamie Laing and BBC regular Yasmin Evans, arrivals will kicked off at 4.30pm.
Meanwhile, the international YouTube Live Stream of the show is set to be hosted by US entertainer and YouTube favourite Todrick Hall and Strictly Come Dancing babe Vick Hope from 7.45pm.
Some of the world’s biggest stars have already been confirmed to play at during the awards show.
As well as British chart-toppers Sam Smith and Jess Gylnne, international pop sensation Pink will be at the bash to collect the Outstanding Contribution to Music Award.