The 27-year-old 'Bleeding Love' hitmaker released 'Lovebird' as the second cut from her latest album Glassheart on December 9, but the track didn't register on the UK's official singles chart, reported Mirror online.
The 200th track on the chart during that week sold 600 copies, meaning Lewis's latest cut sold less than that, making it her lowest-selling single ever.
"This is a bitter pill to swallow for Leona and there is no sugar-coating it. The single was strong and should have done better but, unfortunately, there was no real marketing force behind it," a source said.
"Also, it wasn't released as an official second single. Rather it was pushed out on what is known as an 'impact day'.
Crucially, it didn't capture the imagination of radio bosses and got little airplay. Most people, unless they have the album, have never heard the song.
"It's a little embarrassing for the label because they have invested so heavily in Leona. Having said that, the album did really well and the main thing for Leona is that she's really proud of all the tracks. There are no fillers," the source added.
Lewis's third studio album Glassheart reached number three in the UK back in October.