AceShowbiz - Reality TV star Spencer Pratt has issued a public apology to estranged wife Heidi Montag for the "pain and anguish" he caused during their break-up - and admits he "let her down". Montag walked out on her former "The Hills" co-star in May and filed for divorce in July, citing irreconcilable differences.

Pratt, who has recently been threatening to release sex tapes featuring his former partner, has now reached out to Montag to apologize for his behavior. He tells People.com, "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. I horribly embarrassed the one person that meant the world to me. For my outrageous and infantile behavior, I offer Heidi my most sincere apologies."

"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."