Prime Minister Tony Blair (search), who is struggling to pass a sweeping new anti-terrorism law, insisted Wednesday he was acting on the advice of Britain's security services and would not water down his proposals.

Defending his Prevention of Terrorism Bill (search), Blair said authorities needed the power to act swiftly against suspects, if there were reasonable grounds to suspect they planned a terrorist attack.

Opponents have amended the legislation and say the government must have stronger evidence before it can impose so-called "control orders" on terror suspects, including house arrest, curfews, and electronic tagging without trial.

"It is perfectly obvious in this country that we face a terrorist threat of the like we have never faced before," Blair told the House of Commons. "We need these control orders on the basis of reasonable suspicion of engagement in planning or plotting terrorist activity."

He said he simply could not accept an amendment made by the main opposition Conservative Party in the House of Lords Tuesday, to raise the burden of proof. The Conservatives insist judges must be "satisfied on the balance of probabilities" before imposing the control orders.

"If I were to accept the suggestions that he is making, I would be doing that in contradiction of the express advice I have received and I will not do it," Blair said, in a heated debate with Conservative leader Michael Howard.

Blair faces a battle to get the legislation onto the books. Critics of the legislation say it erodes fundamental civil liberties, including the right to a fair trial and have made several amendments in the Lords, Parliament's upper chamber.

Bowing to opposition, the government has made some concessions, agreeing that a judge be involved in all stages of issuing the orders. Originally it had planned to give a Cabinet minister the power to impose the orders, without involving the courts. The government also said the law would have to be reviewed by Parliament annually.

But Blair said he would not bow to demands that the legislation expire in November, and that the burden of proof be increased.

Although the government has a large enough majority in the House of Commons to overturn any amendments passed in the Lords, it does not have enough time for a drawn out argument. It is rushing to replace anti-terror legislation that Britain's highest court has condemned for breaching human rights. That law expires March 14.

Lawmakers in the Commons will debate the amendments later Wednesday and the bill will return to the Lords.