Pithani Satyanarayana was one of the two former Cabinet colleagues of Kiran who played a key role in the formation of JSP on the united Andhra Pradesh platform in early last month.
Three days ago, he met TDP president Chandrababu Naidu and expressed willingness to join his party.
He formally joined the TDP in the presence of Naidu at the latter's residence here this afternoon.
"I am joining the TDP without any conditions or seeking a ticket to contest the coming Assembly election," Pithani said.
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The ex-Minister said he joined the TDP in deference to the wishes of people of his native West Godavari district.
Pithani is the seventh Minister of the erstwhile Cabinet of Kiran to have joined Telugu Desam Party in the last one month.
Meanwhile, another former minister and vice-president of JSP Sake Sailajanath is expected to leave Kiran.
Sailajanath, who recently underwent surgery in the US for cancer, has never taken part in the JSP activities though he was appointed its vice-president last month. He is said to be considering the option of joining the TDP.
Both are also vice-president of JSP but had not been seen with Kiran in recent days.
MP G V Harsha Kumar, the fifth vice-president of JSP, announced yesterday he would sail with Kiran despite an invitation from Congress General Secretary Digvijaya Singh to return to the parent party.
The sixth vice-president of JSP Undavalli Arun Kumar, who is also an MP, is staying on with the the fledgling outfit.