The reality TV star had threatened to release three raunchy films of Heidi - who he separated from in April after a year of marriage- if she refused his pleas to rekindle their romance and make a new television programme, but claims he is now repentant over his actions.
He said: "I horribly embarrassed the one person that meant the world to me. For my outrageous and infantile behaviour, I offer Heidi my most sincere apologies."
Spencer's divorce from the blonde beauty will be finalised on Valentine's Day next year (14.02.11) and he admitted he lashed out because he found the process so upsetting.
He explained: "Divorce can be a trying, draining, and emotionally devastating experience for all involved. Despite these hardships, most individuals manage to conduct themselves with dignity and maturity. I did not - I failed spectacularly."
The 26-year-old former Hills' star also took to twitter to beg the 23-year-old beauty for forgiveness.
He wrote: "Over the years, her love, support, and Friendship were always given, but never properly cherished. I let her down. She never deserved the pain and anguish I put her through, and although I don't expect it, I hope in time she'll be able to forgive me.
"Even though our relationship has changed, I will always count her among my best friends."