In a setback to the Bharatiya Janata Party in Arunachal Pradesh, all but one of its nine legislators on Monday joined ruling the Congress.

Led by the leader of the Opposition Kameng Dolo, the eight of the nine BJP MLAs resigned from the party and sought Speaker Setong Sena's recognition, which he quickly gave.

An Assembly bulletin said the speaker ordered that the eight BJP MLAs be deemed to be members of Congress as they constitute more than two thirds of the nine-member BJP legislature party.

With this, the strength of Congress rose to 41 in the 60-member state Assembly. The Arunachal Congress has two MLAs, Nationalist Congress Party and BJP one each, one unattached and 14 Independents.

Besides Dolo, the other BJP MLAs who joined Congress are Tapang Taloh, C T Mein, Balo Raja, Tani Loffa, Kipa Babu, Techi Hemu and Bosiram Siram. R T Khunjuju is the only BJP MLA remaining in the party.

Talking to PTI at his residence, Dolo, who was a former deputy chief minister, said they had decided to join Congress to strengthen the hand of Chief Minister Dorjee Khandu.

Dolo said Khandu, who revolted against his predecessor Gegong Apang and replaced him as chief minister on April 9, had "done a lot" by extracting financial packages from the Centre for revival of apex cooperative bank and PDs in the state which his predecessor had "failed."

BJP came to power in Arunachal in 2003 with Congress defectors when NDA was in power at the Centre. This was the first time the saffron party had ruled a state in the North-east.

But the saffron party lost power in 2004 just before the Assembly elections with Apang deserting BJP and joining Congress which came to power at the Centre.

BJP won nine seats under the leadership of Dolo who became the first leader of the opposition in the state Assembly.