Ms Tirath, 59, a Delhi veteran and a prominent Dalit leader, said she had quit the Congress because she was unhappy about the way the party was functioning.
"There has been a change in the thought of the Congress. Traditions have ended," she told NDTV. The "people below" have changed the atmosphere. There is no hearing for complaints even in cases of "harassment," she said.
As the coup played out on live television, an embarrassed Congress claimed that Ms Tirath was upset at not being given a party ticket for the assembly elections in Delhi next month.
Ajay Maken, who is leading the Congress' campaign in Delhi, was addressing the conference when Ms Tirath met Mr Shah. He admitted that he had "just been told" and said, "It shows the desperation of the BJP, they have to import leaders from other parties because they have no faith in their own leaders."
She had contested the national elections from Delhi last year and lost to the BJP's Udit Raj, who was present today when she joined the party and said with Ms Tirath on board, the party will now "aim to win at least 10 if not all of the 12 reserved seats."
After Kiran Bedi and Shazia Ilmi, Ms Tirath is the third prominent woman leader to join the BJP in less than a week.
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