Anil K. Antony, son of veteran Congress leader A.K. Antony, joined the BJP on Thursday, prompting his teary-eyed 82-year-old father to say he was pained by the “wrong decision” and pledge to fight the BJP-RSS till his last breath.

“The decision is really painful…. I don’t know how I will live (after this). But till death, I will be a Congressman,” the senior Antony told reporters in Kerala, hours after his son joined the BJP in Delhi.

The joining of Anil, which came on the BJP’s foundation day, was projected as a big catch by the saffron-party. BJP chief J.P. Naddaand commerce minister Piyush Goyal welcomed Anil, describing him as a “very grounded political worker” who “stood the ground for the nation”.

The BJP, desperate for a foothold in Kerala, feels the veteran Congress leader’s son joining will help the party grow in the southern state.

Anil joined the BJP two months after he resigned as the Kerala Congress’s social media cell chief, protesting against the party’s stand on the controversial BBC documentary on Prime Minister Narendra Modi whose screening has been barred by the government.

Asked if he had consulted his father before joining the BJP, Anil said: “This is not about personalities; this is about difference of opinion and ideas. I strongly believe that I have taken the right step. My respect for my father will remain the same.”

Anil said in Hindi that while many Congress leaders and workers felt that their “dharma” was to “work for a family”, his “dharma was to work for the nation”.