Independent MLA Rambir Shokeen on Tuesday formally withdrew his support to Arvind Kejriwal led Delhi government, bringing down the strength to 35 in the 70-member house.
Shokeen met Lt Governor Najeeb Jung on Tuesday and conveyed his decision to withdraw support.
Shokeen had gone to meet the LG yesterday but could not meet him as he was busy in a meeting and had sought an appointment for Tuesday.
"I have officially withdrawn my support to AAP led Delhi Government and have given it in writing to LG," Shokeen said after his meeting with LG.
Shokeen said he withdrew support as the government has "failed" to fulfil the promises made before the polls.
Shokeen, who was elected from Mundka constituency, said Chief Minister Arvind Kejriwal made several promises on power and water problems in Delhi, but even after several days in office he failed to address the issues.
"We had given support to the AAP based on the issue of removing unnecessary restrictions on villages, extension of 'Lal dora' boundaries, making the teachers working on contract permanent and also on the water issue, but they have failed on all these fronts.
Shokeen said that he along with Vinod Kumat Binny and Janata Dal-United MLA Shoaib Iqbal had met the Chief Minister on February 4, and the latter had assured them of starting work on the issues they raised but "nothing has been done so far."
Shokeen further blamed Kejriwal and his ministers of not visiting the villages of Delhi at least once after the formation of the government.
In a House of 70, AAP's strength was reduced to 26, after Laxminagar constituency MLA Vinod Kumar Binny was expelled from the party and another member was elected as the speaker.