The Central Bureau of Investigation (CBI) Saturday arrested Bansal's nephew Vijay Singla and three others in Chandigarh for allegedly taking a bribe for the promotion of the railway official.
Singla, a businessman who is Bansal's sister's son, his friend Sanjay Goyal and two others are being brought to New Delhi for further investigation.
Singla allegedly accepted Rs.90 lakh for the promotion of a railway official.
Bansal said in a statement that a "close relative" had been arrested but added that he had no business dealings with his nephew.
The Bharatiya Janata Party described the Congress-led United Progressive Alliance (UPA) regime as a government of "wheelers and dealers".
"Every day new instances of shameful corruption are coming out. The embers of 2G and Coalgate are yet to subside, now we have railwaygate.
"This government is no more a government of the common man. It is the government of wheelers and dealers, and it is a government of brokers and middlemen."
He said the government was mired in controversies and Prime Minister Manmohan Singh was himself "under a cloud of corruption".
"It is happening because the prime minister is under a cloud of corruption in coalgate.
"All the ministers are enjoying his and (Congress president) Sonia Gandhi's protection and are looting the country. What is happening in the railwaygate is a symptom of that," he added."The topmost assignment in the railway board is now being negotiated for sale."
He also sought the prime minister's resignation.
"The BJP is duty bound to reiterate that you please resign as the PM of India because you do not have any moral right to govern because India is increasingly getting established as the most corrupt regime under you," the BJP spokesman said.