The elected members belonged to the Gorkha Janmukti Morcha (GJM) which is spearheading the ongoing movement in the hills for a separate Gorkhaland state.
GJM general secretary Roshan Giri said that the resignations would be forwarded to the GTA principal secretary.
Giri had stated yesterday, "We have decided to resign from the GTA."
GTA has been turned into a "farce" by the West Bengal government, he alleged and said that GJM and the people of the hills would fight for the single agenda of a separate Gorkhaland state.
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In the June 20 meeting, all the political parties and public organisations of the hills had unanimously declared their support to the longstanding demand for a separate Gorkhaland state in north Bengal.
The GJM has been ruling GTA since 2012 and its five-year term is set to expire this month.
A tripartite agreement paving the way for the setting up of the GTA, an elected body for the Darjeeling hills, was signed in 2011. The parties to the agreement were the union home ministry, the state government and the GJM.