Rashtriya Janata Dal leader Lalu Yadav
Narendra Modi, set to be India's next prime minister, will receive no congratulations from one man - Lalu Yadav.
"I can't offer congratulations to Modi. I am not an opportunist," the Bihar politician declared.
Prime Minister Manmohan Singh was among the first rivals to wish Mr Modi as trends emerging from the counting of votes for the national election showed a BJP sweep.
Tamil Nadu Chief Minister Jayalalithaa, who had sparred with the BJP leader during the campaign, also offered her congratulations.
Lalu Yadav, who has always been one of Mr Modi's fiercest critics, had last month controversially taken Mamata Banerjee's cue to compare the Gujarat Chief Minister to a "butcher".
"Even a butcher is ashamed of Narendra Modi. Should this person become the PM of India?" he said.
Lalu, head of the Rashtriya Janata Dal or RJD, contested the election in Bihar in alliance with the Congress, which has been routed across the country.
The RJD leader has suffered embarrassment on his home turf with his wife Rabri Devi and daughter Misa Bharti both losing in Saran and Pataliputra. He had worked hard in these constituencies as these were prestige battles for him.
Mr Yadav had won from Saran in 2009, but was defeated in Pataliputra by Nitish Kumar's Janata Dal-United.
He did not contest this time as his conviction in a corruption case meant he cannot fight elections for a few years.