Two Congress MLAs had previously resigned on January 25 and joined the BJP.
As of Monday, five Congress lawmakers have resigned, and a sixth was earlier disqualified for anti-party work.
Puducherry assembly has 30 members and three nominated members.
Ahead of the trust vote, Narayanasamy claimed majority based on his request to the speaker to not allow the three nominated members to vote.
Since past apex court orders have allowed nominated MLAs to vote, the Puducherry speaker allowed them to vote.
The Congress-led coalition was on Sunday left with 12 MLAs while the opposition has 14 MLAs.
The Congress had won 15 seats in the 2016 polls and came to power with the support of three DMK and one independent member. Opposition AIADMK has 4 MLAs, All India NR Congress seven and the BJP three nominated MLAs.
Puducherry Congress Crisis Deepens As Another MLA Quits Before Floor Test
ndtv.com - get the latest breaking news, showbiz & celebrity photos, sport news & rumours, viral videos and top stories from ndtv.com Daily Mail and Mail on Sunday newspapers.
Puducherry floor test: CM meets Congress, DMK MLAs to discuss strategy
oneindia.com - get the latest breaking news, showbiz & celebrity photos, sport news & rumours, viral videos and top stories from oneindia.com Daily Mail and Mail on Sunday newspapers.