"As the party convenor, he has failed badly, because of which the party has suffered defeat in one election after another," the Chandni Chowk MLA said in a statement.
Delhi's ruling AAP, which came to power in 2015 with a landslide victory by bagging 67 out of 70 Assembly seats, was third in the triangular contest in the Lok Sabha polls with the BJP being the winner.
On five of the seven Lok Sabha seats, the Congress came second. Three of the AAP's seven candidates also lost their deposits as they scored less than one-sixth share of the votes as per law.
Lamba, a former Congress leader, said the party has removed her from its official WhatsApp group.
"From day one I was saying the same thing which you said today. I was sometimes added to the group, sometimes removed. Instead of doing this, it would have been better if you (Kejriwal) have raised above this and discussed the issues and resolved them," she tweeted in Hindi.
Without naming anybody, she said the one who took decisions behind closed doors should be held responsible.
"At a time when the party came third and its candidates lost their deposits, the responsibility lies with the one who took all the decisions behind closed doors" she said.
( With inputs from IANS )