After meeting with Karnataka governor Vajubhai Vala, Mr Azad said the Congress and the Janata Dal (Secular) have adequate numbers to form the government and that the coalition would provide a stable government.
"Should honourable governor invite BJP that means you are openly inviting horse-trading, inviting defection in the parties and under the constitution, as the head of the state of Karnataka, you should not," Mr Azad told reporters.
The BJP has won 104 seats, eight short of a clear majority of the 222 seats on which the election was held. The Congress won in 78 and Deve Gowda's JDS in 37. Karnataka has 224 seats. The Congress has extended support to the JDS.
Mr Azad said the BJP laying claim to form the government for being the single largest party holds no good. "Because there is Supreme Court judgement in the case of Goa wherein the Congress emerged as the single largest party, but the BJP in coalition with small parties was able to show the adequate numbers," he said.
"The court held that it was not necessary that the single largest party can claim if a group of parties have adequate numbers to be sworn-in," Mr Azad said.
The Congress and the JDS have submitted separate letters to the governor seeking an invitation to form the government in the southern state, Mr Azad said.
The Congress and the JDS were unable to enter into a partnership ahead of the election results in Karnataka. The Congress' Chief Minister Siddaramaiah, who was voted out on Tuesday, split from the JDS over a decade ago and the acrimony between him and Deve Gowda remains unmitigated.
With inputs from PTI