Louis Walsh stands in for Cowell on The X Factor USA

Louis Walsh is filling in for Simon Cowell on The X Factor USA today. Cowell is in bed suffering from bronchitis so he flew his Irish pal over to Kansas City to cover for him, according to The Sun.

Walsh was in Manchester yesterday at auditions for the UK show with fellow judges Gary Barlow, Mel B and Tulisa Contostavlos when he was called by Cowell. An X Factor insider told The Sun:

Louis will stand in today and tomorrow, sitting alongside the US show's judges Britney Spears, Demi Lovato and LA Reid.

This is the second time Louis has stood in for Simon: he previously took his place at the Birmingham auditions of Britian's Got Talent in 2010.

Simon hopes to be well enough to attend the next set of audition in San Francisco on June 16.

Meanwhile back in the UK, tensions between Walsh and X Factor judge Gary Barlow continue to grow.

They argued over an 18-year-old singer who Gary loved and Louis thought was rubbish. Gary Barlow is reported to have said:

Barlow did appear to enjoy working with new judge Mel B. He tweeted this cosy picture of the pair, saying they were "two peas in a pod."