According to The Mirror, the former Spice Girl angered audience members by refusing to put through a singer named Katie who had proved popular with the crowd. It is thought that Halliwell had the casting vote after the budding star was backed by Cheryl Cole and Louis Walsh but rejected by Simon Cowell.
A source told the newspaper: "Geri had the chance to please the crowd and many were shouting Katie's name. But Geri ignored them and turned Katie down, causing the crowd to go crazy.
"Eventually they invited Katie back to try again, but Geri was judged to be the executioner and she never recovered from that."
Meanwhile, the Daily Star claims that Halliwell also annoyed fans by adopting a "mean" judging style, prompting a chant of "Bring back Dannii! Bring back Dannii!" in reference to absent panellist Dannii Minogue.
Halliwell was the first of several guests to stand in for Minogue while she takes maternity leave. Pixie Lott has been tipped to take over the post in Birmingham on Monday.