Tamang was attacked with sharp weapons when he was overseeing preparations for a public meeting at Clubside in the heart of Darjeeling town on May 21, 2010.
NIA probe: Bimal Gurung demands grilling of Binay Tamang, Anit Thapa in connection with Gorkhaland protests
Gurung claimed that Binay Tamang had taken crucial decisions without consulting him or the GJM central committee.
The state had accused its northern neighbour of giving shelter to the GJM supremo who is wanted in several cases including Unlawful Activities (Prevention) Act) (UAPA), murder, rioting and arson.
Gurung has been evading arrest since August when cases were lodged against him under the stringent Unlawful Activities (Prevention) Act for his alleged involvement in several bomb blasts in Darjeeling
Tamang blamed party supremo Bimal Gurung for violence in the hills and said the people of the region "will not allow Darjeeling to turn into Kashmir".
Rival Gorkha Janmukti Morcha factions led by party chief Bimal Gurung and chief coordinator Binay Tamang are fighting a bitter war of attrition to garner support of residents of the Darjeeling.
Shops and markets opened in the hills, defying the indefinite bandh sponsored by the Gorkha Janmukti Morcha (GJM) for a separate Gorkhaland.
Ousted leader Binay Tamang on Sunday challenged GJM chief Bimal Gurung to "come out of hiding" and lead the Gorkhaland movement from the front.
West Bengal Minister Gautam Deb has accused the Sikkim government and police administration of helping Gurung and his associates to flee.
The police had yesterday issued a lookout notice against the GJM chief for his alleged involvement in various cases, including a bomb blast in Kalimpong police station which killed one volunteer.
Tamang said the state government had sent a letter in his name to attend the August 29 meeting but that he had refused to go.
Gurung expressed his willingness to hold talks in a letter, a copy of which was made available to the media today.
According to sources, the unknown assailants lobbed the grenade and slipped into the alleys that lead to different parts of the town.
The court, however, directed that charges be framed against all other 47 accused, including Gurung's wife Asha and several other top leaders of GJM.
Gurung's comment came ahead of an all-party meeting on July 6 where the newly-formed Gorkhaland Movement Coordination Committee is slated to take a call on the ongoing agitation in the hills.