Government-proposed measures to combat terrorism have been branded "unlawful" and "intolerable" by senior experts.
Both Lords are concerned at the three-month detention plan
Plans to detain suspects for up to three months and a glorifying terrorism offence were criticised by Law Lord, Lord Lloyd of Berwick and Lord Steyn.
In an interview for the BBC's Panorama, Lord Steyn, a former Law Lord, warned people's liberty was being endangered.
On Thursday, the home secretary said the ban on glorifying terrorism was being revised in light of criticisms.
People would have to "intend to incite" further acts of terror to be convicted, Charles Clarke said.
Opponents had said the original proposal was unclear and could threaten civil liberties. Mr Clarke denied plans were being "watered down".
The plan to detain terror suspects for up to three months without charge would stay, the home secretary said.
Lord Steyn said that new power would be found to be unlawful, and incompatible with the European Convention on Human Rights.
"Experience shows that governments frequently ask for more powers than they need and when they get those powers they abuse them from time to time," he said.
He said the glorification of terror offence this would also be unlawful and in breach of human rights laws.
"We live in a country that Voltaire called 'the country of liberty': isn't that being endangered?" he said.
Lord Lloyd of Berwick, who carried out the inquiry into terrorist legislation for the Conservative government in 1995-6, said of the new Bill: "It says that a person commits an offence if he glorifies, exalts, or celebrates an act of terrorism whether in the past or in the future.
"Now to me that is a very odd provision.
"I have never seen anything like it in an Act of Parliament.
"And I pity the poor judge who's going to have to explain those words to a jury - glorify, exalt or celebrate.
"Presumably they all mean something different otherwise you wouldn't have three words instead of one.
"Somebody in the Home Office must have thought they mean something different.
"But how is a judge going to explain the difference between those three things?
"The essence of criminal law is that it should be clear and it must be certain.
"Having an offence couched in this language will in practice be unenforceable."
Charles Clarke denied the revision of the law was a climb-down
On the detention proposal, Lord Lloyd said: "It begins to look ... a little like internment.
"And it would certainly be seen that way by some ethnic minorities.
"Fancy being kept for three months without being charged. Being questioned notionally and not being charged.
"That is intolerable.
"By, in a sense, stirring up the fear, and then saying well this is what we're going to do about it by legislating here, there and everywhere, I think that's in a sense irresponsible."
Panorama, Blair v Blair, will be broadcast on BBC One on Sunday 9 October 2005 at 22.15BST