PATNA/NEW DELHI: Bihar chief minister Nitish Kumar on Monday called Narendra Modi an expert in "jhooth ki kheti" (cultivation of falsehood) while BJP said there is a question mark over his mental state, as the attack against each other touched a new low after JD(U) ended its alliance.

Kumar slammed his Gujarat counterpart over his charge of 'criminal negligence of security' at his rally in Patna last month that was rocked by serial explosions leaving six people dead. BJP was also accused of telling "white lies". "The incidence of serial blasts at the rally in Patna was most condemnable ... But terrorists in a way helped BJP, otherwise its rally at Patna was flop in terms of size of crowd," he told reporters in Patna.

"Had the blast not happened, everybody would have talked about the thin attendance at the " hunkar rally " for which BJP leaders had claimed it would be unprecedented in terms of size," Kumar said after the "Janata Ke Darbar me Mukhya Mantri" programme.

He was reacting to Modi's barbs against him during a poll campaign in Chhattisgarh last week. The BJP's prime ministerial candidate had said that while blasts were taking place in his rally here, the "insensitive" Bihar chief minister was "feasting" at the JD(U) convention at Rajgir.

"He has again gone wrong. I had cancelled my scheduled programme at Munger on October 27 to attend an international yoga convention and had proceeded to Rajgir from there. It's on record, anybody can check," Kumar said without naming Modi.

Hitting out at BJP for accusing him and Bihar government for security lapses at the rally, he denied the charge and said by repeating it they were following Hitler's advice that if a falsehood is repeated it becomes the truth.

He accused Modi of being an expert in "jhooth ki kheti" (cultivation of falsehood). Kumar also rubbished accusations by BJP that he had prevented policemen from arresting Indian Mujahideen founder Yasin Bhatkal in July and questioning him.

"It's a white lie. Is such decision taken by a chief minister or is it the decision of police and security force in such a situation? BJP leaders were heaping these accusations on him to gain space in newspapers and TV channels". Kumar's remark that Patna blasts had helped BJP left the party fuming which said it had doubts about his mental state.

BJP spokesperson Meenakshi Lekhi went on to add that Bihar needed more mental health institutes.

"I can only say that there is a question mark over the mindset ... the mental state of Nitish Kumar," she said at a press conference in Delhi.

She said Bihar is lagging behind in several aspects and mental health institute is one of them. "The state needs more mental institutes," Lekhi said.

