Geri Halliwell reportedly texted Mel B a sarcastic "congratulations" message after the star appeared at the UK X Factor auditions after her.
The former Spice Girl stood in as a guest judge on the hit UK TV show alongside Gary Barlow, Louis Walsh and Tulisa Contostavlos last month. Mel was invited to do the same role at auditions last week.
Simon Cowell is yet to find a permanent replacement for former judge Kelly Rowland and reports surfaced that Geri was the favourite to take the coveted job.
However, sources say the star is annoyed at her competitors - especially former bandmate Mel.
"Geri was gutted her guest role didn't become permanent. She's told pals she texted Mel saying: 'Congrats on getting my job!' It's a bit odd - as Mel hasn't got the permanent role," a source told British magazine Closer.
Other stars including Nicole Scherzinger, Leona Lewis and Rita Ora have also guest starred on the judging panel. Mel is said to be ignoring Geri's taunts.
"Mel's told pals that she has nothing against Geri. She hopes it will blow over," the source added.