Former Uttar Pradesh Congress party chief Rita Bahuguna Joshi joined the ruling Bharatiya Janata Party, which forms the federal government, just before elections in the state early next year.
The 67-year-old Joshi attacked Congress vice-president Rahul Gandhi for the manner in which he has been running the party and his reaction to the Indian army's "surgical strikes" on jihadist staging posts in Pakistan-administered Kashmir.
"India is fighting terrorism and the Modi government has given the army a free hand. Besides valour of the army, the government's strong leadership was also behind the surgical strikes.
"Along with the nation, I too was happy. The whole world accepted India's arguments behind the strikes. Congress, however, behaved like a small party and went on to question it. The whole nation was upset with a phrase like 'khoon ki dalali' (peddling of blood)," she said referring to Gandhi’s controversial comment in the aftermath of the strikes.
Joshi, daughter of late Congress veteran Hemvati Nandan Bahuguna, joined the BJP in the presence of party chief Amit Shah in New Delhi.
She said, "The decision to quit Congress was not easy. However, I took it in the interest of the nation and the state (UP)."
Joshi reportedly became upset after the Congress decided to project former Delhi chief minister Sheila Dikshit as its chief ministerial face in Uttar Pradesh.
Her joining the BJP is expected to give a boost to the party's efforts to consolidate the Brahmin vote as it looks to capture power in the state after a gap of more than 15 years.