"They will regret the decision to part ways with us and ask themselves as to why they had done so," Jaitley told BJP workers at a state-level function here without, however, identifying any party.
The event had been organised as part of the drive to collect iron and related material for construction of a statue of independent India's first Home Minister, Sardar Vallabhbhai Patel, in Gujarat. The statue is the brainchild of Gujarat Chief Minister Narendra Modi.
The senior BJP MLA in Bihar Assembly, Ashwani Chaube, will not have to carry out his threat to resign from the House as BJP will do well in the general elections on 40 seats in Bihar, Jaitey added.
Jaitley sought to downplay the threat to BJP from Congress or a likely Third Front configuration, saying that Congress does not inspire confidence among the people while the Third Front was a "losers' front".