Congress, he alleged, helped Lalu walk out of jail and indulged in all sorts of backroom deals with him but refrained from acknowledging the relation in public as they feared it would dent their votes outside.
"Is it not a fact that mother and son helped Lalu to get out of jail (on bail after being convicted for five years in the fodder scam)" the BJP Prime Ministerial candidate asked at an election meeting here.
"Having got Lalu released from jail, why cannot they share a stage with him at a rally" he asked.
"Does not this maa-beta have alliance with Lalu Did not they help him come out of jail Then why do they refuse to sit together with him... They tell him don't sit with us or we will be wiped out from the country. Isn't it a deception, a sin," he asked as he urged voters to teach them a lesson.
He said "none can save the maa-beta (mother and son) from certain defeat.
Slamming the UPA government as "weak" and "remote controlled" by the Gandhi family, he said that a "dead" government could not do any good for the country which needed a strong government to solve complex problems through decisive leadership.
Reaching out to electorate in the crucial state, where BJP aims to make big gains to realise its dream of capturing power in the Centre, the BJP's prime ministerial candidate said Bihar was blessed with the goddess of knowledge which Gujarat lacked.
"Wherever we go, we find IAS, IPS officers from Bihar. But the goddess of wealth is yet to come here. It does not come without lotus," he said, referring to his party's symbol which is also associated with the goddess of wealth.
Referring to the poor state of banana farmers in the region, Modi said their counterparts in Gujarat are doing much better economically due to his government's policies and similar steps would be taken by BJP government to help them if it is elected to power.
Referring to the legacy of the legendary socialist leader and former Bihar chief minister Karpoori Thakur, Modi said, "He worked tirelessly all his life for the welfare of the downtrodden sections of the society.
"I seek his blessings to complete his incomplete work," he said.
Modi said, "Please ensure that the Congress and RJD don't get to open their account in Bihar."
Regretting that the UPA government had wasted ten precious years and wanted to stop the BJP-led NDA from coming to power, Modi said the country could not afford instability or misrule any more and urged the people of Bihar to give the finishing touch to the NDA's strong performance in the Lok Sabha elections.
Modi also recalled the Patna serial blasts at his October 27 rally in Patna.
"I am lucky to have survived the Patna serial blasts to be with in your midst ... Had the God been not with me, I would not be here," he said.
Recalling scenes of blood splattered around the Gandhi Maidan on that day, Modi hailed the valour of the huge number of people who attended it depite the blasts taking place one after another.