Senior leader Basavaraj Horatti formally joined the BJP in the presence of Chief Minister Basavaraj Bommai and other party leaders on Wednesday.
The induction was a low-key affair at Bommai's R T Nagar residence.
Besides Bommai, former CM Jagadish Shettar, BJP national general secretary C T Ravi, Ministers R Ashoka, Govind Karjol, and C C Patil, among others, were present.
A mega event will be held in Hubballi to mark Horatti's entry into the BJP, Bommai said.
"His entry will be a big strength for the BJP, especially in north Karnataka," the CM told reporters. "He has been a lawmaker for the last 45 years and no one such a record in the entire country. We will use his experience and will give him all the opportunities and respect he deserves," he added.
Horatti, who was previously with the JD(S), resigned as chairperson of the Legislative Council. He also resigned as MLC. He is likely to get the BJP's backing to contest the upcoming MLC election from the Karnataka West Teachers' constituency.