Slomiansky, 70, was named as the Jewish Home MK accused of improper behavior by Hagit Moriah-Gibor, a party activist, on Facecook last December.
Moriah-Gibor gathered a number of other women who made similar complaints against Slomiansky.
Police began an initial probe against Slomiansky immediately after he was named as a suspect, even though no criminal complaint was ever filed against him by any of his accusers.
Police announced Thursday that there was enough evidence to launch a full criminal investigation into the matter.
Slomiansky has denied all wrongdoing.
However, he issued an apology for any unintentional offense he may have caused.
“If any woman was insulted, hurt or felt uncomfortable because of my behavior, I apologize and I would apologize to her face, from the bottom of my heart, if I knew who she was.” He added that his “well-known loving nature may have been misinterpreted.”