Lohan's publicist, Leslie Sloane-Zelnik, confirmed the post by Lohan was legitimate.
"If you have something to say to me, say it to my face - that's what I have believed my whole life - don't be a coward and say it to others first, let alone all the media in the world," Lohan wrote.
The father and daughter have publicly quarreled for years. Lohan said in the dash-happy blog post that she tried to make things work in hopes "of having a father again" and "wanting things to change" despite what her mother and siblings have gone through with him.
Lohan continued: "Having said that - the people were right, and he is yet to change - but this time, without his daughter by his side - he has become a public embarrassment and a bully - to my family, my co-workers, my friends and a girl that means the world to me (it's obvious who that is)."
The "Mean Girls" star went on to say that she believes her father is addicted to fame, and if he really cared about her, he would respect her wishes. She also said than Ronson and Lohan's mother Dina would never "sell me out." Lohan ended the post by saying that she had a therapist and it's not a cameraman at x17 (the celebrity photo agency and Web site).
In a separate post, Ronson said she was angry when she first heard about Michael's attack on her and called him a man "who is so desperate for attention that he goes to the media whenever possible." Ronson went on to say she felt "no need to publicly defend my role in Lindsay's life - I'm just sorry that she likes me more than him."
After the blog entries were posted Thursday, Michael told OK! magazine in an exclamation point-heavy statement that his concerns about Ronson were all generated by ex-wife Dina, who stars alongside their 14-year-old daughter Ali in the E! reality series "Living Lohan." Michael called Dina a "money-loving, fame-seeking, self-serving deceiver."
"All I want is for Lindsay to be healthy and in a good relationship," he also said in the statement. "I want her to use the gifts she has in the best ways and to help others! I said it from the very beginning: Show me who you walk with and I will tell you who you are! People may deceive us, but our eyes and facts don't! OPEN YOUR EYES!!!"
Michael, a former Wall Street broker, married Dina in 1985. They settled a long-simmering divorce in August, though they returned to court in New York earlier this year over custody issues. Michael was released from prison in March 2007 after serving nearly two years for attempted assault and driving while intoxicated.