Opposition on Thursday slammed the Lokpal Bill saying it would lead to "constitutional havoc" as the centre would be encouraged to "usurp" rights of states through the provision of setting up of Lokayuktas.

Initiating the debate in the rajya sabha, leader of the opposition Arun Jaitley also opposed minority quota in the Lokpal bench, inclusion of NGOs and keeping CBI out of the purview of the ombudsman.

"If you are creating history, let us not create bad history. We will be leaving a lot of task for the next generation to do," he said.

He made it clear the the BJP would not support the Bill in the present form. "Please accept amendments that the colleagues have moved," he said.

Going clause-by-clause in the Lokpal and Lokayuktas Bill, 2011, Jaitley said the ombudsman was "designed to be vulnerable to constitutional challenge. Let us create an institution which is constitutionally possible."

Referring to the provision on the setting up of Lokayuktas in the state, the BJP leader and noted lawyer said it would lead to creating "a grey area" by which the centre can usurp powers of states. "Why are you creating a constitutional havoc? The government is trying to make constitutional cocktail," he said.

Jaitley said the government wants to subvert an institution even before its creation. "You want to kill it in the womb," he alleged.

"You wanted to create a phoney Lokpal and create a smokescreen that you are giving a constitutional status," he said taking a jibe at the proposal that was included at the instance of Congress general secretary Rahul Gandhi.

Jaitley said his party objected to three "absurd and unworkable" provisions of the bill.

With regard to CBI, Jaitely wanted it to be under the purview of Lokpal with a directorate of prosecution. "An effective Lokpal needs an effective investigating agency like the CBI. You are creating a Lokpal so that it becomes a rudderless institution," he charged.

He also opposed inclusion of NGOs and trusts within the purview of Lokpal, saying it was "revenge provision" and would create a system which would be intrusive in the private life.

"I don't think members of this house will support you on this," the BJP leader said.

On the provision for quota of "at least" 50 per cent for minorities in the 9-member Lokpal bench, he said it was to designed to make the law "vulnerable to constitutional challenge", as somebody could move court.

The government has majority in the 5-member panel that would appoint the Lokpal. And then the power to remove is vested with the Supreme Court, which can be approached by only the government.

"If Lokpal is biased in favour of the government, the beneficiary of the bias will decide if an appeal can be filed against the appointment," he said.

Jaitley said his party was for a strong and independent Lokpal but opposed a "weak and phoney" anti-graft ombudsman.

Contending that the government has brought a weak Lokpal, Jaitley said the house should on Thursday pass a Lokpal bill only after accepting the amendments brought by the opposition for strengthening of the institution.

"When passing this law, we have to decide if we will collide with history or write new history," he said.

"I regret to say this is a half-hearted legislation," he said adding the legal architecture was not enough to fight corruption.

Jaitley said Lokpal institution has been weakened by the government keeping firm control over investigating agencies like CBI.

"You wanted to make it a toy and then say it has constitutional status," he said, adding his party was for constitutional status for the Lokpal if the bill does not attack rights of the state.

"There is no contradiction between fighting corruption and federal system," he said.

Stating that it was a test before opposition parties if they will help in passage of a weak bill or help bring amendment, Jaitley threw a challenge to the allies of the ruling UPA if they were willing to strike for a strong Lokpal.

"...if they are only willing to proclaim or are they willing to strike," he said.

Jaitley earlier said the investigation mechanism proposed in the bill is such that a probe can never be completed.

"Criminal investigations are never done in a round-robin (manner)," he said, adding that opposition's demand was just to make CBI an impartial investigating agency.

He said chairman of Lokpal should be included in the panel to select CBI director.

The opposition Leader said the government has deliberately brought a law which is constitutionally vulnerable.

"You want to kill the Lokpal when it is still in the womb ...lets not create a bad history," Jaitley said adding the amendments proposed by opposition would remove the deficiencies in the bill.

"We will pass a Lokpal, (but) not your (government) Lokpal," he said.

Seeking a relook and rethink on the bill, S C Mishra (BSP) said it is "totally illegal" and a "fraud" on the Constitution and will be struck down by the court. "We should not make laws under pressure," he said.

Rejecting Singhvi's contention that centre can enact laws under Rule 253, which can be applicable to the whole country or in parts to cater to international treaties like the UN convention, Mishra wondered whether the government wants to control all state subjects through this provision.

"It will completely ruin the federal structure", he said wondering whether the centre was planning to clamp emergency in the country.

Sitaram Yechury (CPI-M) said the spirit of the constitution must be kept in mind while framing the law and added that the government should accept the amendments to make a stronger Lokpal Bill.