The 39-year-old star spent the evening chatting with the 'Angels' singer about paranormal activity and when he asked if he could stay over, she agreed but didn't want any ''funny business'' so was stunned when she returned from getting changed to discover Robbie waiting in just his pants.
Kerry - who split from first husband Brian McFadden in 2004 - told new! magazine: ''Apart from Brian the closest I've got to a celebrity s**g is Robbie Williams, no less. We met backstage at 'Saturday Night Takeaway', soon after my split from Brian.
''Rob obviously took a shine to me as he asked if he could come to my hotel room that night.
''I was dead nervous - I called me mum and she told me to shave my legs but I wasn't thinking about anything like that!
''Sure enough, at 10pm he was outside my door. He came in and we chatted for hours about all things paranormal and spooky.
''Next thing, he asked if he could stay the night - in my mind not for any funny business. So I said yes, went to put on my PJs, came back and he was by the bed wearing just his Y-fronts!
''I thought he was about to give me a personal rendition of 'Rock DJ'. I got so flustered I started dusting. Seriously!''
The former Atomic Kitten star - who has two daughters with Brian and three other kids from previous marriages - confessed to enjoying a ''little smooch'' with Robbie but things never went any further.
She added: ''I was fully clothed, and although we had a little smooch, I'd no intention of taking it any further. And I think when Rob realised that, he was on his way.
''I love Robbie to bits and it always makes me chuckle to think how close he came to being one of my very few celeb conquests.''
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