Now it seems an official version of the song, credited to the Libertines, does exist.
And you can download it here. (thanks to Niali from the libertines.org.uk forum).
Recorded in 2003 during the 'Don't Look Back Into The Sun' sessions with Bernard Butler producing, the song features Carl Barat on vocals, but Pete Doherty does not feature.
The cover was leaked online by a music industry figure who works in licensing/publishing (well, surely not McFee).