Agartala: Five-time Congress legislator in Tripura Ratan Lal Nath, who last month joined the Bharatiya Janata Party (BJP), lost his assembly membership under the anti-defection law, Speaker Ramendra Chandra Debnath said here on Friday.

"As Ratan Lal Nath left Congress and joined BJP on December 22, his assembly membership would be disqualified from that date under the Schedule 10 of the Constitution (which deals with the anti-defection law)," Debnath told IANS after issuing an order on Friday.

"State Congress President Birajit Sinha, in a letter, informed MER that Nath had joined BJP and also demanded he be disqualified him from the assembly membership. I have served two notices to him (Nath) to attend the hearings of his case. But Nath informed that he was unwell.

"With prior notice, I have taken ex-parte decision on Nath's disqualification. This is for the first time in the history of Tripura a sitting member was disqualified under the anti-defection law," he said.

Welcoming the Speaker's decision, Congress state Vice President Tapas Dey said: "Opportunistic politics must be curbed and value-based politics must be upheld."

After months of hobnobbing, Nath, former Opposition Leader of Tripura assembly, joined the Bharatiya Janata Party on December 22 last year in the presence of the BJP's General Secretary Ram Madhav, Assam Ministers Himanta Biswa Sarma and Parimal Sukla Baidya, Tripura BJP President Biplab Kumar Deb and a host of party leaders.

The 71-year-old Nath held various posts in Congress and since 1993, was elected five times as Congress candidate from the Mohanpur assembly constituency in western Tripura.

With this, the Congress strength in the outgoing assembly has been reduced to just two from the original ten.

The Communist Party of India-Marxist led Left Front has 51 members with the CPI-M alone having 50 legislators.

Nath along with six other MLAs, who deserted the Congress to join Trinamool Congress and then moved to the BJP, voted for the National Democratic Alliance's nominee Ram Nath Kovind in the presidential election on July 17 last year.