Ramesh, whose party has only six members in the Upper House, got maximum 106 votes out of the three candidates who were in contention.
"It is a victory of morality against arrogance," Ramesh said.
Sources said the entire opposition, including the Congress, supported Ramesh's candidature.
The victory comes days ahead of the election to the post of deputy chairman of the Rajya Sabha where the opposition is contemplating to field a common candidate.
The PAC comprises of not more than 22 members, of which 15 are from the Lok Sabha, seven from the Rajya Sabha.
MPs from both the houses elected members of the PAC from among themselves through election.
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