A CID inquiry was ordered and the police registered a case of rape against H Halappa who quit as Karnataka Minister following a charge of sexual assault made by his friend's wife.
As opposition mounted pressure for Halappa's arrest, Chief Minister B S Yeddyurappa announced a CID probe, saying "let the truth come out. Whoever is guilty should get punishment".
In Shimoga, police registered a case of rape against Halappa after the victim formally lodged a complaint.
The FIR would be forwaded to CID in Bangalore, Shimoga District Superintendent of Police Murugan told reporters.
The Congress staged a day-long dharna in the state capital and protested in parts of the state demanding the immediate arrest of Halappa who resigned after a media report that claimed he had sexually assaulted his friend's wife.
A delegation of Congress leaders called on Governor H R Bhardwaj and presented him a memorandum demanding dismissal of the state government and CBI probe into the issue.
Yeddyurappa flayed the opposition for raking up the issue even after Halappa's resignation and ordering of CID probe and wondered why the issue was being raised days before next week's gram panchayat elections when the incident had allegedly taken place in November last year.
"There is no doubt that it's a conspiracy," state unit BJP president K S Eswarappa said.
"Police will take action s per law. We will not pre-empt, we will not prompt or side-track anything" Home Minister Dr V S Acharya said after discussions with DGP Ajay Kumar Singh.
Halappa has dismissed the charge as baseless and said it was a political conspiracy to defame him.