"Netaji had called Nitish and Lalu and congratulated them for their victory," a party leader said.
SP state chief and Uttar Pradesh Chief Minister Akhilesh Yadav and senior party leader Shivpal also congratulated the grand alliance for its thumping victory in Bihar.
"Congratulations to Nitishji and Laluji on their historical victory," Akhilesh posted on Twitter.
SP was initially part of the grand alliance but later pulled out of the grouping and contested the Bihar elections alone. The party did not win even a single seat.