A senior official at the Delhi assembly said Chandni Chowk MP Vardhan, South Delhi MP Ramesh Bidhuri and West Delhi MP Parvesh Verma resigned as MLAs.
"All the three MLAs who were elected to Lok Sabha submitted their resignation to the assembly Speaker M S Dhir," he said.
With the resignation of the three MLAs, BJP's strength in the assembly has come down to 28 from 31.
Vardhan, who has been made Union Health Minister, won from prestigious Chandni Chowk Lok Sabha seat defeating AAP's Ashutosh and Congress' Kapil Sibal.
Verma defeated Jarnail Singh of AAP by a margin of 2,68,586 votes in West Delhi parliamentary constituency. He had won the assembly polls from Mehrauli constituency.