Agartala, March 10 (IANS): The Congress Monday alleged that lakhs of infiltrators have illegally settled in Tripura during the 31-year rule of the Left Front government.

During the heated debate over the issue of infiltration from across the border, Tripura Chief Minister Manik Sarkar told the state assembly that during the past three years (2011-13) out of the 6,356 infiltrators, 4,695 illegal entrants have been pushed back into Bangladesh.

"Lakhs of Bangladeshi infiltrators have settled in Tripura during the 31-year rule of the Left Front government. These illegal migrants have managed government documents to reside in India under the patronage of the ruling Left parties," senior Congress leader Ratan Lal Nath told the assembly.

Quoting Sarkar's statement, Nath said: "Your (CM's) statement also proves that 1,661 illegal infiltrators have not yet been pushed back and they settled in Tripura in the past three years."

The issue rocked the ongoing budget session of the Tripura assembly Monday.

"Due to the unchecked infiltration, the indigenous tribals have become more marginal. The Left Front government is actually not concerned about the interest of the tribals," the Congress leader said.

The Congress legislators demanded identification of the infiltrators under the Foreigners' Act 1946 and pushing them back into Bangladesh.

The chief minister told the agitated opposition members that after the infiltrators were detained, they were sent to court and under its direction they were pushed back.

The Bharatiya Janata Party (BJP) has also blamed the government for not taking proper action against the illegal infiltrators.

Tripura shares an 856-km border with Bangladesh and a large portion of it remains unfenced and porous.

There is a large number of thickly populated Bangladeshi villages and towns on the other side of the international border, making patrolling by the border guards a delicate task.