A day after resigning from the Bharatiya Janata Party (BJP), veteran tribal leader Nand Kumar Sai on Monday joined the ruling Congress in Chhattisgarh where the Assembly polls due this year-end.

Addressing mediapersons after joining the Congress, Sai said it was a tough decision for him to quit the BJP and claimed it was no longer the party which it used to be "during the time of Atal ji and Advani ji”.

Sai submitted his resignation to state BJP president Arun Sao on Sunday and claimed his colleagues were hatching conspiracies and levelling false allegations to tarnish his image, which had left him deeply hurt.

The 77-year-old leader, a former three-term Lok Sabha member and three-time MLA, served as the BJP's state president in both Chhattisgarh and undivided Madhya Pradesh in the past and has considerable influence in tribal-dominated parts of Surguja division (northern Chhattisgarh).

He joined the Congress on Monday in the presence of Chief Minister Bhupesh Baghel, party's state chief Mohan Markam and ministers at Rajiv Bhawan, the party state headquarters here.

Sai said, “The BJP's form has changed. It was a tough decision of my life (to quit the BJP) as I was associated with it since the Jana Sangh time. I have worked with Atal ji (former prime minister Atal Bihari Vajpayee), Advani ji, Sushma Swaraj ji and other senior leaders and followed them." "The party is no longer in that form which it used to be during the time of Atal ji and Advani ji. The circumstances seem to have changed,” he claimed.

Sai said before quitting, he was not holding any position in the BJP and was an ordinary worker.

"I don't want any post. Even if they don't give a post in the party, they can at least ask how party affairs should be operationalised. I did not have any problem with the party. The party is not important, but the important thing is that everyone (party members) should work together for the common people," he said.

"I decided to join the Congress as it has been doing good work under the leadership of Chief Minister Bhupesh Baghel ji," Sai said.

In Baghel government, efforts are being made for the uplift of poor, backward, tribals and all sections,” he added.

When reporters asked former state chief minister and senior BJP leader Raman Singh if the party would suffer a loss, he said whenever a senior worker quits, the organisation faces a loss.

“The party has always respected Sai. He was the Lok Sabha member. He was also sent to the Rajya Sabha. He also became chairperson of the National Commission for Scheduled Tribes (NCST). Even after that he has taken such a decision," Singh said. "He (Sai) is a senior leader and he knows everything about politics. I express my best wishes to him for joining the new team,” Singh said.

Sai, a prominent tribal face of the party who hails from north Chhattisgarh, was first elected as the Janata Party MLA in 1977 from Tapkara seat (now in Jashpur district) in Madhya Pradesh.

In 1980, he was elected as BJP's Raigarh district unit chief. He was elected as the BJP MLA from Tapkara in 1985 and 1998.

He was elected to the Lok Sabha from Raigarh in 1989, 1996 and 2004 and the Rajya Sabha in 2009 and 2010.

Sai was Chhattisgarh BJP president from 2003-05 and MP BJP chief from 1997 to 2000.

He was first leader of opposition in the Chhattisgarh Assembly after the state was carved out from MP in November 2000.

Sai was appointed as the NCST chairperson in 2017.

He was close to late BJP leader Lakhiram Agarwal and the duo had played a crucial role in the establishment of the saffron party's foothold in Chhattisgarh.

When the Assembly elections were held for the first time in Chhattisgarh in 2003, Sai decided to contest against then Chief Minister Ajit Jogi from Marwahi seat instead of his traditional seat Tapkara. Though Sai tasted defeat, the BJP formed then government in the state.

Sai has often grabbed limelight for criticising various decisions of the previous 15-year-long Raman Singh-led BJP government in the state.

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