BJP on Friday attacked the government in Rajya Sabha on unilateral ban on export of cotton saying it has affected farmers and triggered suicides as cotton prices have fallen sharply and questioned whether the step was taken to favour private traders.

Demanding a statement from the Government on the issue, the members staged a walkout.

Raising the issue during Zero Hour, senior party leader M Venkaiah Naidu said unilateral ban on cotton exports and the "ambiguity with regard to its lifting" has resulted in a sharp fall in cotton prices causing severe hardships to cotton growers.

"The ban was imposed on March 5 and lifted on March 12 but certain conditions were levied and as a result not even a tonne of export was done...lakhs of bales are lying piled up in Andhra Pradesh, Maharashtra, Karnataka and Gujarat. Prices have come down to Rs 3,500 from Rs 6,000 (per quintal) government should remove the ban unconditionally," he said.

The situation has worsened to such an extent that "farmers are committing suicides and a farmer in Maharashtra, who committed suicide, left a note saying don't vote for Congress and NCP," Naidu said.

His remark drew sharp reaction from Congress members, including Renuka Chowdhary, that culminated into acrimonious exchange of words between the treasury and Opposition benches.

Naidu said even the Cotton Corporation of India had not come forward to purchase cotton from farmers while the prices have fallen even below its minimum support price.

He said he had come to know that Agriculture Minister Sharad Pawar had written a letter to the Prime Minister Manmohan Singh on the issue but was not aware of the facts.

"Entire country wants to know at whose behest the ban was imposed...do you want to help private traders," he asked, triggering protests by the treasury benches.

The entire BJP then rose, shouting slogans "jawab do, jawab do".

All attempts by P J Kurien, who was in the Chair, failed to pacify the agitated members, who demanded a reply by the government.

Minister of State for Parliamentary Affairs Rajeev Shukla said, "The Commerce Minister has already spoken on the issue ...still I will convey the issue to Commerce Minister and Textile Minister."

Naidu, however, was adamant that a reply on the issue be made in the House on Monday while members rose on their feet demanding that the government should tell at whose behest the ban was imposed.

"Why has the government become so insensitive," Naidu posed before the BJP members walked out.