Congress MP SPY Reddy on Friday joined YSR Congress party, saying it is the only party sincerely working to keep Andhra Pradesh united.
The MP from Nandyal on Friday night met YSR Congress president YS Jaganmohan Reddy and joined the party.
Later, SPY Reddy told reporters that he would meet Lok Sabha Speaker Meira Kumar on Saturday to submit his resignation to oppose the Congress decision to carve out separate Telangana state.
He said YSR Congress alone was trying sincerely to keep the state, and recalled that Jaganmohan Reddy went on hunger strike in jail for a united state.
Jaganmohan Reddy, the MP from Kadapa, was released on bail on Tuesday.
He was in jail for nearly 16 months in a disproportionate assets case.