The X Factor winner told the Daily Star that she provided vocals for the Calvin Harris-penned hit before relinquishing the song to the Bajan singer.
Lewis said: "I worked with Calvin and we recorded 'We Found Love' but he went touring with Rihanna and she ended up releasing it.
"I didn't commit to it because I wanted 'Trouble' to be my first single, so I think that was another reason they went with Rihanna.
"It was the same version and production but mine's better."
'We Found Love' has sold 6.5m copies worldwide and reached the number one spot in 25 countries, making it one of the most successful tracks in recent years.
Lewis added: "I still have the recording but I'd never leak it. That's so unprofessional.
"There are so many songs I've recorded, only to hear other people singing them. It happens all the time. It was a bit annoying to see how big a hit it was around the world but if I'd released it maybe it wouldn't have done as well."
Lewis's third studio album Glassheart is released today. Last night, she performed a selection of tracks from the record as part of a promotional set at London's G-A-Y.
Listen to Lewis's latest single from the LP, 'Trouble', below: