Labour MP Mr Chris Mullin said "every sensible person" shared Mr Tony Blair's desire to see the perpetrators of the Omagh atrocity and their supporters behind bars.
But he argued there was no substitute for patient detective work resulting in credible evidence and the conviction of the right people.
"If we get this wrong, we shall end up creating a political base for a tiny isolated sect that at the moment has no political base." Mr Mullin pressed Mr Blair to consider accepting two amendments tabled by him to ensure there was "credible evidence, capable of belief in court". He asked that measures be introduced to enable the RUC to take audio recordings of interviews with suspects and that a solicitor be present during interviews.
"Will you make this Bill conditional on that happening? Because you will find that if you do, all the mainly bogus objections raised to these matters will melt away like the snow on a volcano if they are a condition of being allowed to go out and arrest people in the way that the Bill proposes."
Mr Blair stressed that the situation now was different. "We are dealing with a very, very, small group of people who really have no base and support, but who do have the capacity, as we've seen, to engage in the most appalling acts of terror."
Audio recording was now the law and to deal with points of the European Convention on Human Rights, it was now a condition that people have to see a solicitor, Mr Blair said. ". . .We are acutely conscious of the need to steer a path between carefully targeted action and action that could result in a miscarriage of justice." Mr Mullin said: "I do have grave misgivings about this Bill. It bears all the hallmarks of being conceived in haste and I fear we may repent at leisure, as we did with internment."
Mr Tony Benn, former Labour Cabinet Minister, pleaded with Mr Blair to take a "historical perspective".
He spoke of previous anti-terrorist legislation but claimed the "only gain there ever was" was when the present government opened negotiations with nationalists, leading to the Belfast Agreement.
Mr Benn said: "May I urge you not to take any action that might look as if it was going back to some of the old legislation which was repressive, was ineffective and didn't contribute."
The Prime Minister said the measures were targeted carefully and took account of the possibility of a backlash in the republican community. Mr Blair emphasised two big differences in the current situation - "one, that we march in step with the Irish Government . . . a huge difference from anything that has gone previously . . ." And the government was now dealing not with terrorist groups "with actual real support" but people who "have no support anywhere."