Louis has been a big fan of Jack's throughout the competition, so it was no surprise to hear the 22-year-old was not happy when his favourite was booted out of the show on Saturday night.
In a big twist, Simon Cowell announced there was going to be a shock double elimination on the X Factor this weekend and the person with the lowest number of public votes would be sent home instantly from the competition.
Following Saturday night's live performances, Mel B lost another act as Jack was revealed as the finalist with the fewest votes.
On finding out Jack had been sent home, Louis tweeted: "Gutted. Don't think he was given a fair chance with his songs. #xfactor."
Earlier on in the evening, Jack didn't seem to impress the judges with his rendition of Leona Lewis' 'Bleeding Love'.
While Louis Walsh said he thought Jack was "a small room performer", Simon told Jack he needed to work a lot harder to make it in the industry. Unhappy with the panel, after watching Jack's performance himself, Louis took to Twitter to defend the hopeful.
He said: "Still need to find the right song for @jwaltonmusic and to get rid off all the gimmicks! He's best with his guitar with a current song!!"
The 1D singer has been avidly following the talent show this year and Louis was recently spotted at the X Factor studios, offering his expertise to the contestants.
Heading back to the studios ahead of Saturday's live show, Louis made sure to join Jack at his rehearsal to help him perfect his performance.
Jack has since said he was chuffed to have Louis' support and revealed the popstar had told him, he would continue to look out for him as he builds his career in the music industry.
Speaking to The Metro, Jack said: "Louis encouraged me to work hard. He suggested I don't stop and he genuinely does believe in me. He said if I ever need anything, he will look after me."
Meanwhile, Cheryl Fernandez-Versini was the second judge to lose an act as Lola Saunders was the second finalist to leave the show in the double elimination.
Facing Stereo Kicks in the sing off, Lola and the boyband had the judges torn on who to send home. After going to deadlock, Lola was eliminated as she had received the fewest public votes.
The X Factor continues this Saturday and Sunday (8-9 November) at 8pm on ITV.
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Watch Jack's performance of 'Bleeding Love' here: