The former glamour model dated the singer from 1998 to 2000 and when they both attended the EnergySave Christmas bash, Katie, 38 - who is married to Kieran Hayler - made a rambling speech to her fellow guests about Dane.
A source told the Daily Mirror: ''Katie was meant to be with hubby but arrived on her own. Everyone was surprised there was no Kieran with her.
''They were very touchy-feely.''
In a video obtained by the newspaper, Katie can be heard telling the guests, ''Can I just say something, my ex-boyfriend actually got me the job tonight - Dane Bowers - the love of my life.''
Katie previously spoke out about her regret at taking an overdose after she split from Dane, 37, in a ''stupid'' attempt to win him back.
Katie admitted that at the time she was young and foolish and before their break-up she had wrongly convinced herself that Dane had a developed a huge crush on Victoria Beckham when they worked together on the August 2000 single 'Out Of Your Mind', even though Victoria was married to soccer superstar David Beckham.
She said: ''Lots of people try and do things make their exes jealous. But at the end of the day they've seen what you're really like, so if you try and look different or go with their mates if they don't want to know you they don't want to know you.
''When I was younger stupidly enough, I wanted my ex Dane Bowers back and stupidly I took an overdose to get him back - you do these things for attention. It is a massive thing, it does not work, but I was young and naive, if anyone was speaking to me just do not do it.
''He worked with Victoria Beckham and I thought something was going on, I thought 'is he obsessed with her?' It ended up being her friend so my paranoia was right.
''I was so heartbroken and I used to say he was the love of my life, I used to say that without realising because I now consider Kieran to be the love of my life. Dane broke my heart but it only made me stronger. It has helped me to deal with certain situations. I think having your heartbroken is an awful feeling, you can't explain it.''
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