On the run since June last year, Mr Gurung, who has Unlawful Activities (Prevention) Act charges against him and a lookout notice, said in Delhi, "Our demands are within the framework of the Constitution. We have nothing against West Bengal. But our culture and traditions are different."
Reiterating that he will continue his crusade for the Gorkhas, Mr Gurung said, "Our movement is for the Gorkhas and I hope the truth wins."
On all the cases filed against him, he said, "have trust on judiciary and am ready to co-operate with any independent organization into any investigation."
After weeks of trouble that erupted in May last year over Mamata Banerjee's announcement that teaching of Bengali would be made compulsory in the hills of Darjeeling - a decision that was later withdrawn - Bimal Gurung had fled, to Sikkim, according to West Bengal police.
A segment of his own party turned its back on him. He was suspended and his one-time lieutenant, Binay Tamang, replaced him as party chief and head of the Gorkhaland Territorial Administration, the autonomous body in charge of the administration of the Darjeeling hills.
Binay Tamang has called Bimal Gurung's return "a political drama".
"When we began talks with the West Bengal government, Gurung said we had sold out the Gorkhaland cause. Now he says he is ready to speak to the West Bengal government. What does this mean? He is just out to create trouble at a time when Darjeeling is peaceful and normal," Mr Tamang said.
The Trinamool leader in charge of north Bengal and Darjeeling affairs, Gautam Deb, accused the BJP of playing games. "The BJP is encouraging these separatist elements. Bimal Gurung is an accused in the eyes of law. How can he show up in Delhi? People in Darjeeling won't accept him," he said.