"Top party leaders including Modi are responsible for it (defeat)," the outspoken MP from Begusarai Lok Sabha constituency told the media here.
"The BJP was not defeated in Bihar, it committed suicide," he added.
The Grand Alliance led by Chief Minister Nitish Kumar routed the four-party combine of the Bharatiya Janata Party in the elections to the Bihar assembly despite aggressive campaigning by Modi.
Bhola Singh said the rampant use of unparliamentary language by Modi and other party leaders during the campaign harmed the BJP, leading to its defeat.
"During the campaign, local BJP leaders were sidelined and ignored," he said.
"There was no logic to raise issues such as beef and that firecrackers would be burst in Pakistan if the BJP loses. All this resulted in our defeat," he said.
The BJP leader said the party failed to make 'roti-rozi' the main campaign issue though it spoke of economic development as its top agenda.
Bhola Singh is the fifth BJP MP from Bihar to hit out at the party leadership after Sunday's humiliating electoral loss.
The four MPs who spoke publicly earlier are Shatrughan Sinha (Patna Saheb), Hukum Deo Narain Yadav (Madhubani), RK Singh (Ara) and Ashwani Kumar Choubey (Buxar).