Reality television star Spencer Pratt has apologised to his estranged wife Heidi Montag for his 'outrageous and infantile behaviour'.

'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,' contactmusic.com quoted Pratt as saying.

Pratt, whose divorce will be finalised on Valentine's Day next year, admits he lashed out because he found the process so upsetting.

'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,' he said.

The 26-year-old also took to Twitter to beg Montag for forgiveness.

'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,' Pratt wrote on his Twitter page.

'Even though our relationship has changed, I will always count her among my best friends.'