Who is the first Indian Prime Minister who did not belong to the Congress party at any time in his political career?

AB Vajpayee was the first Indian Prime Minister who had never been a member of the Congress party at any point in his political career. While Charan Singh and Chandrasekhar were Congress members before leaving the party, and Deve Gowda was also never in Congress, Vajpayee became Prime Minister first in May 1996 (though his initial term lasted only 13 days, he later served a full term 1999-2004).