"It is totally unconstitutional. There is no such provision in the NCT Act. If L-G decides to go for secret ballot, we will oppose it," DPCC chief spokesperson and senior eader Mukesh Sharma said.
There were some reports that under a provision of NCT Act of 1991, L-G Najeeb Jung may offer legislators the option to choose the chief minister via a secret ballot.
AAP had won 28 seats in its debut assembly elections and had later formed the government with outside support from eight Congress MLAs.
The government led by Arvind Kejriwal had resigned on February 14 after the party's pet project, the Janlokpal Bill, could not be passed due to opposition from BJP and Congress.
President's Rule was imposed in Delhi on February 17.