A spokesperson for the company said that the poster, which uses the strapline "Where have all the women gone?", was banned on the grounds that it had the "potential to offend public decency".
Obviously Paddy Power's official stance on this is personal affront and they said to the press "We are completely astonished by the reaction of the London Underground to our advert. Fun is central to the Paddy Power brand and we strive to communicate this in all of our advertising."
However, they're well known for controversial ads and having a quick look at their blog (yes Paddy Power have a blog) they're less astonished and more aware of the extra publicity they'll get from the ban:
"The Man Boob ad seems to be causing particular offense with several companies, including Dublin Bus and the London Underground, refusing to run it in its uncensored hairy nippled glory.
"Of course all this fuss helps the ad to do exactly what it was intended to do by drawing attention to PP Bingo, so it's doing its job admirably.
"Is it all that offensive though? We show a bit of man boob and people begin to squirm in their seats. Unlike some previous ad campaigns which were run with the full awareness that they would cause controversy and debate, this new series was seen as being a bit cheeky but well within the modern scope of what is politically correct. Or so we thought."
Personally, I think they're right. The ad stopped me in my tracks for a few seconds when I originally saw it in Metro or londonpaper. It's got minor shock value. But I completely forgot about it and didn't have a compulsion to rush out and play bingo or call the decency watchdogs.
How it could offend public decency is beyond me. But then again quite a lot could "potentially" offend public decency, especially as far as the Tube is concerned.