6:05 PM PT -- A Weinstein rep tells TMZ, "It's insanity to suggest that Harvey Weinstein had any involvement in this."

The law firm Paz de la Huerta fired in the Harvey Weinstein case is now going after another lawyer who allegedly tried to steal the Weinstein case and compromise de la Huerta's rights by attempting to get copies of her psychotherapist records under false pretenses.

Tensor Law claims in a new lawsuit, obtained by TMZ, a lawyer named Michael Rubin contacted Paz shortly after her allegations against Weinstein became public. He allegedly said he was a victims' rights attorney who could help her more than anyone, but one thing he needed was her medical records.

The suit claims Rubin browbeat de la Huerta to fire Tensor Law, which she did. The suit says de la Huerta did not give Rubin the records, and now Tensor Law says Rubin was up to no good from the get-go -- he was trying to make de la Huerta waive her right to keep the records secret.

The suit does not specifically claim Rubin was working for Weinstein ... Tensor Law says Rubin was either working for Weinstein or felt he would get rewarded by Weinstein if he produced results for him.

The suit also claims Rubin went to the Manhattan District Attorney to try to convince prosecutors not to criminally charge Weinstein.

Tensor claims ... because the firm was fired it missed out on tens of millions of dollars in potential contingency fees that would have been generated from lawsuits against Weinstein for allegedly raping de la Huerta and getting her fired from "Boardwalk Empire." The firm says there were other suits as well.