Union Power Minister Piyush Goyal on Monday termed the passage of Constitutional amendment bill, which paves the way for Good and Services Tax (GST) regime, in the Lok Sabha, as a big bang reform.

"GST getting passed in Lok Sabha is a big bang. If this is not big bang, then what will be," he said at the launch of book "Modi And His Challenges" by economist Rajiv Kumar.

Parliamentary approval was accorded to the bill when the Lok Sabha passed the bill, as the Rajya Sabha had passed it last year.