Kat Von D has alleged that Jesse James cheated on her with at least 19 women.

The pair split for the second time in a year in September. They rekindled their relationship in August after calling off their engagement in July.

There has been much speculation surrounding the end of the romance, with suggestions that Jesse had been unfaithful to his former fiance.

Kat has now put rumours to rest in a lengthy Facebook blog titled Thank You, Jesse James'. The raven-haired tattoo artist took to the social networking site to claim that Jesse had romanced other women during their relationship.

"Today I encountered the 19th girl to add to the list of people Jesse cheated on me with during this last year," Kat wrote in the public letter.

"I kept going back and forth in my mind as to what the best way would be for me to release and let go of any residual feelings remaining from that toxic relationship. All of this may sound petty or immature to some, but I assure you this is coming from a place of pure honesty and love."

Jesse split from his wife Sandra Bullock last year, after a string of women alleged he had affairs while married.

Kat attempted to prove people wrong about her former lover, but admits she was ultimately fighting a losing battle.

"There was a time when I was confident and excited at proving the world wrong, because I believed so deeply in people's ability to change for the better," she wrote.

"Although this was not a primary purpose in the relationship, I did feel like it would be a positive thing for those who judged Jesse solely based on what they read in tabloids, to see that change is always possible - even in the people who seem hopeless."

Despite the adamant message in the blog, Kat remained reflective of the relationship. The star wished Jesse well.

"I think it just made me sad today to imagine him still in that dark place - where seeking validation through the attention of women takes precedence over being a good father, a sincere friend, a better co-worker, and a happy individual," she wrote.

"Time is something you can never get back, and what we do with this very present moment is the most real thing we have. So if that's the lesson Jesse forced me to face and learn by all of this, than all I can say is Thank You," she added.

"It would be nice to move on now, and kindly thank you all in advance for your support, love, and positivity."