Kalita was formally inducted into the saffron camp here at party headquarters in the presence of union minister Piyush Goyal, BJP General Secretary Bhupendra Yadav and Rajya Sabha MP l Baluni.
Goyal hailed Kalita's decision to resign from Congress and Rajya Sabha despite being party's chief whip as "bold" and said he left the grand old party on the issue of national interest.
"He left the Congress on issues based on principles. He supported the government's move of national integration by abrogation of Article 370. We requested him to join BJP and contribute to nation-building. We will be benefitting from his long experience as a parliamentarian. His coming to BJP will also help the party in Assam and the Northeastern states," he said.
Kalita hailed the BJP top leadership and slammed the Congress for its stand on Article 370.
"The country is marching ahead under the leadership of PM Modi and BJP chief Amit Shah," he said.
Kalita said he talked to the party leadership on the issue of Article 370 but they were clueless and directionless.
"When it comes to national integration, all parties should support the government. As a member of the Congress, I couldn't oppose Article 370 in Rajya Sabha. That's why I decided to resign from the membership," he said.
Yadav said Kalita joined the party expressing confidence on the leadership of Modi.
He said the party would get constructive benefits from Kalita's parliamentary experience and his orgsational skills would help the party in increasing its strength in Northeastern states.
Kalita, who was also party's Chief whip in Rajya Sabha, was upset with the Congress when he was asked to issue a whip to party members against the government's move on the Kashmir issue.
Kalita was a Rajya Sabha member from Assam. He had only a few months left in his tenure and was due to retire on April 9, 2020.
Kalita contested the last Lok Sabha elections from Mangaldai constituency but lost to BJP's Dilip Saikia.
Born at Rangiya in Kamrup (Rural) district of Assam, Kalita was elected to Rajya Sabha for the first time in 1984 and was reelected again in 1990. He was elected to 12th Lok Sabha in 1998. He was again elected to Rajya Sabha in 2008 and 2014.
Kalita is the second Congress MP from Rajya Sabha to resign from the grand old party after Sanjay Singh, a member of the erstwhile Amethi royal family. Singh also joined the BJP a day after resigning from Congress.
( With inputs from ANI )