Samajwadi Party supremo Mulayam Singh Yadav, on 7 December, inducted Amar Singh in the party's parliamentary party board.
This comes three months after Mulayam appointed Singh as national general secretary of the Samajwadi Party.
Singh, who was earlier expelled from the party for six years, has been facing the wrath of Uttar Pradesh Chief Minister Akkhilesh Yadav.
He had last month met Mulayam to lodge a formal protest in this regard.
"I don't want to hurt him, but the insults have gone beyond the limit of my tolerance," Singh had said.
"My heart is full of pain, will talk to Mulayam Singh ji. Mulayam ji was the one who stood by me against his son publicly," he added while referring to Akhilesh.