During a party conference in Bangalore at the weekend, Sonia Gandhi urged party workers to prepare for an election.
Her Congress Party will launch a series of street protests and rallies against the 18-party ruling coalition led by Atal Behari Vajpayee.
The political crisis facing Mr Vajpayee over the scandal has worsened, with confrontations both inside and outside parliament forcing the adjournment of Monday's business.
Congress Party spokesman Jaipal Reddy said the campaign would begin on Saturday. "It is a long haul programme. How long it will be will depend on Mr Vajpayee," he said.
But Mr Reddy ruled out holding a vote of no confidence in parliament.
The BBC's Susannah Price in Delhi says the government, which has a majority of 20, would almost certainly win any such vote.
During a party conference in Bangalore at the weekend, Sonia Gandhi urged party workers to prepare for an election.
"Let the message go forth from Bangalore that we will fight every battle, wage every war, make every sacrifice to ensure that the country is liberated from the shackles of this corrupt, shameful and communal government," she said.
Parliament uproar
Earlier, security guards moved in to separate rival members of parliament who were threatening each other outside the building.
In parliament, opposition MPs chanted "The PM is a thief" and "The government is making commissions, while soldiers are bleeding".
Parliament has not functioned since last Tuesday and some believe it will remain paralysed for the rest of the week.
So far two cabinet ministers have resigned - including Defence Minister George Fernandes.
No resignations
But the government has gone on the offensive with Mr Vajpayee vowing to fight back against the opposition campaign.
He has announced a major rally next Sunday and his government has challenged the opposition to a debate in parliament, saying it is willing to prove its majority on the floor.
And senior officials from the prime minister's office have rejected calls to resign.
The principal secretary to the prime minister, Brajesh Mishra, said he would not step down and added that the allegations were baseless.
An army court of inquiry has begun an investigation into the allegations.
Several defence ministry officials have already been suspended.