A self-confessed ex-madam who claims disgraced former Gov. Eliot Spitzer was a frequent client, vowed Monday to run against him for state comptroller if he throws his hat in the ring.

Kristin Davis, who served prison time for running a high-priced Manhattan call girl ring, said she would push to legalize marijuana and prostitution.

“I will run firstly to highlight the inequities and sexism in our criminal justice system which penalizes women, minorities and poor people while wealthy, connected white men like Eliot Spitzer evade justice,” Davis wrote on her blog.

Spitzer is teaching a class at City College and writing an online column in an apparent bid to rehabilitate his image following his resignation as governor in March 2008 after it was revealed he patronized high-end hookers.

Last week, The New York Post reported that Spitzer is considering running for comptroller, a seat now held by fellow Democrat Tom DiNapoli. Gov. David Paterson backed the idea.

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Davis wrote a book in which she said Spitzer was a repeat customer, though she was not involved in the prostitution ring Spitzer was caught up in before he resigned. After he stepped down, a spokeswoman denied that he was a client of Davis’.

Davis has also threatened to reveal other names in her “black book,” which she said contains politicians, business leaders and pro athletes.

In her blog post yesterday, she said she was once the manager of operations for a hedge fund and “built a multi-million dollar international business out of nothing.”