Diwakar Reddy has been a Congress MLA for several decades now from his native Anantapur district in Rayalaseema.
Speaking on the occasion, Diwakar Reddy said that Seemandhra's development, after bifurcation of Andhra Pradesh, is possible only with Naidu's visionary leadership.
Earlier in the day, the Congress MLA from Vijayawada Yalamanchili Ravi too joined the TDP.
About half-a-dozen ministers in the former Congress government led by N Kiran Kumar Reddy and a number of party MLAs have joined the TDP after the Telangana bill was passed in parliament.
However, the occasion could be taken as an opportunity, he said, adding that the new Andhra Pradesh could be developed in all spheres if everybody worked hard.