Chief Minister Prem Singh Tamang aka PS Golay and two newly-elected BJP MLAs S T Venchungpa and Y T Lepcha took oath as members of the Sikkim Legislative Assembly on Monday.
Speaker L B Das convened a one-day session of the House to administer the oath to the three new MLAs.
Golay, also the Sikkim Krantikari Morcha (SKM) supremo, had won the by-election to the Poklok Kamrang seat, securing 84 per cent of the 12,870 votes polled in the seat on October 21.
By-poll to Poklong Kamrang was necessitated after former chief minister Pawan Kumar Chamling of the SDF vacated it on winning two seats in the Assembly elections held earlier this year.
Venchugpa and Lepcha had registered victories in the by-elections to Gangtok and Martam Rumtek Assembly seats respectively held on the same date.
With the newly-elected MLAs, the strength of the ruling SKM has gone up to 19 while that of its ally BJP is 12 now.
Chamling is the lone Sikkim Democratic Front (SDF) MLA in the House.