The 38-year-old 'Bodies' singer, who welcomed the arrival of his first child Theodora with wife Ayda Fields on September 18, starred as a guest judge with friend and former Take That bandmate Gary Barlow on the series last year.
This week, Williams has been lending support and giving advice to the aspiring hopefuls, including Jade Ellis, Ella Henderson, Union J and Rylan Clark.
The star recently stirred trouble by tweeting his support for controversial act Clark, before adding "VOTE RYLAN" on his official website.
It's thought his allegiance would annoy Barlow, who branded the 24-year-old Essex-born contestant as "embarrassing".
Williams recently stunned viewers when he performed on X factor Italia flanked by topless dancers.
X Factor airs on Saturday night at 8.20pm and on Sunday at 8pm.
See pictures from last weekend's third live results show here: