Bihar Chief Minister Nitish Kumar will launch a signature campaign named 'Shabd Wapasi', demanding that Prime Minister Narendra Modi take back his DNA remark made last month at a rally in Muzaffarpur.

Rashtriya Janata Dal president Lalu Prasad Yadav will also join the campaign and both the party heads will officially announce the launch of the campaign on Tuesday at a press conference, according to reports.

Nitish announced about his campaign on Monday in a series of tweets, in which he said that 50 lakh people from Bihar will sign the 'Shabd Wapasi' campaign and also send their DNA samples. He said that the first phase of the campaign will start on 29 August at the 'Swabhiman Rally' at Gandhi Maidan in Patna, Bihar's capital.

The second phase will begin in September, when they will take signatures of the public. The preparations to send the samples for DNA test will begin at the same time, Nitish tweeted.

Nitish also hit out at Modi for his speech at Parivartan Rally in Gaya, during which he called Bihar a "Bimaru" state.

While addressing a public meeting on 25 July in Muzaffarpur, Modi had targeted Kumar and said: "There seems to be some problem in his DNA because the DNA of democracy is not like that. In democracy, you give respect even to your political rivals".

Nitish Kumar reacted strongly to the remark, saying, "His (Narendra Modi) tone and tenor was unbecoming of a Prime Minister". He asked Modi to take back his words as it insulted not only him, but also the people of Bihar.

"It is indecent on his part and an insult to Bihar and its people... I am a Bihari and Modi has insulted and humiliated all Biharis by questioning my DNA and using such a language," he had said.

Both the RJD-JD(U) alliance and BJP alliance in the state have indulged in war of words ahead of the assembly elections, which is expected to be held sometime between September and November.