Parkar, 45, headed the Kankavli Municipal Council of Sindhudurg district, where the NCP is struggling to get a foothold. The district is a stronghold of Congress minister and former Shiv Sena leader Narayan Rane.
According to sources, Parkar -- once a staunch anti-Narayan Rane activist -- decided to join the Congress "to strengthen the party" in Konkan, still considered a Shiv Sena bastion.
Parkar joined the Congress in presence of Chief Minister Prithviraj Chavan and Maharashtra Pradesh Congress Committee (MPCC) chief Manikrao Thakre at the party office here.
"Parkar has joined Congress as he felt the party is the only one doing constructive work," Rane told reporters here.