He was welcomed into the YSRCP fold by Jagan who offered him a party scarf.
Speaking to reporters, Mohan Reddy accused the TDP leadership, which is in power in Andhra Pradesh, of "losing the grip on the party" and neglecting party workers.
"We have seen a leader in YS Jagan Mohan Reddy and have joined the YSR Congress Party," he said.
According to sources, Mohan Reddy crossed over to the YSRCP, the principal opposition party in Andhra Pradesh, as the TDP leadership was reportedly not in favour of his candidature for the Nandyal Assembly bypoll, necessitated due to the death of the sitting MLA Bhuma Nagi Reddy.
The Election Commission is yet to announce the schedule of the byelection.
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