Quizzed about which 1D star pulled the most girls, Louis, 20, admitted that Harry was more successful than fellow singletons Zayn Malik, 19, and Niall Horan, 18.
'Do I even need to say who?' asks Louis, 20.
'I think it would be completely and utterly unfair to single out girls in that way, or put it like that.
'But...if you were to put it like that, I think it would - possibly - be...Harry.'
Louis and Liam Payne, 18, are happily loved up with their girlfriends so behaved themselves while supporting Big Time Rush earlier this year.
1D are all now back in the US again for a headline tour - but Louis insists they won't be counting the boys' conquests.
'Do we keep a tally? No we do not!' Louis tells the Daily Mirror.
'That's hideous!'
Though Zayn Malik is now dating Little Mix's Perrie Edwards, Louis confirmed that Harry's no longer going out with Inbetweeners star Emily Atack, 22, who he was recently reported to have fallen for.
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