New Delhi, Nov. 24: Finance minister Arun Jaitley today responded to Manmohan Singh's assessment of the demonetisation drive by alleging that the former Prime Minister was unhappy because the "maximum black money" was generated during his rule.

The response capped a day on which BJP sources conceded in private that they did not expect the Opposition unity to last this long.

"Those who did not consider the generation of so much black money and scams during their regime as blunder are now saying the crusade against black money is a blunder," Jaitley told reporters in the Parliament complex after Singh had spoken in the Rajya Sabha.

The finance minister charged the UPA governments with "overseeing the generation of the maximum amount of black money, the largest scales of corruption and the biggest scams".

He accused the Opposition of "inventing and manufacturing reasons to escape the (demonetisation) debate (in the Rajya Sabha)".

"The government's position is very clear from Day One. We are ready for the debate. The Opposition was finding excuses to avoid a discussion. But this morning, they were caught by surprise when we announced that the Prime Minister will participate in the debate," said Jaitley.

He stressed that the demonetisation drive would impact the economy "positively as far as the medium and long terms are concerned". "Lots of shadow money will become part of the banking system," he added.

On a Samajwadi Party MP's charge that while some BJP leaders were aware of Modi's move but not the finance minister, Jaitley said: "This decision was kept a secret. The people who needed to know, knew. In any case, the allegation is contradictory that the information was known to some BJP members as though I am not a member of the BJP."

He rejected the insinuation that RBI governor Urjit Patel did not address the media after the scheme was announced. "Office people are supposed to work and not come in front of cameras," Jaitley contended.

But an official from Jaitley's ministry - economic affairs secretary Shaktikanta Das - has briefed the media day after day on various aspects of the demonetisation.

Jaitley turned down the Opposition's demand for constituting a joint parliamentary committee to look into the scheme, saying "some evidence" or "blame" should exist before one was constituted.

Government sources said they did not expect Parliament to resume work before Tuesday, until the Opposition was over and done with the programme of protests on "Aakrosh Diwas" (Day of Angst) on Monday.

Notwithstanding the façade of optimism, the scale of Opposition unity has stunned the BJP. "It's a warning that we cannot take our adversaries for granted," another minister said, expressing concern over how an issue that "contained elements of economic nationalism and zeal to fight corruption" brought together parties that were "sworn enemies" in their regions.

The BJP's only consolation was its undeclared "allies" - which offer "issue-based" support - such as the Biju Janata Dal, the Telangana Rashtra Samithi and the YSR (Congress) did not throw in their lot with the Opposition.

The BJP MPs were told to fan out in their constituencies, speak to as many people as possible after being armed with talking points proffered by senior ministers. Six ministers, including Jaitley, Rajnath Singh and Manohar Parrikar, were asked to interact with the members in batches of 40 each from today.