Home Secretary David Blunkett wants new anti-terrorism laws to make it easier to convict British terror suspects.
Mr Blunkett is on a tour of the sub-continent
He has discussed lowering the standard of proof required by a court and introducing more pre-emptive action.
Possible plans, revealed on his six-day trip to India and Pakistan, also include keeping sensitive evidence from defendants and secret trials before vetted judges.
But civil rights groups have condemned the proposals as shameful and an "affront to the rule of law".
And a lawyer for Feroz Abbasi, one of the Britons held at Guantanamo Bay in Cuba, said Mr Blunkett's proposals showed he was not fit to be home secretary.
Speaking in Lahore, Mr Blunkett was expanding on a speech he made on Friday in which he said he wanted new prosecuting powers to prevent terrorist acts.
New act merging existing legislation from 2000 and 2001
Burden of proof lowered from "beyond all
reasonable doubt" to "on the balance of probabilities"
Part-secret trials for Britons
Security-vetted judges for sensitive evidence
14 foreign nationals held without trial
His proposals, revealed on Monday, would bring elements of his recent anti-terror legislation into the existing trial system.
The Anti-terrorism, Crime and Security Act 2001 allows foreigners who are suspected international terrorists to be detained indefinitely without charge or trial in the event their lives would be in danger if they were deported.
Britain is holding 14 foreign terror suspects under this law, based on evidence which is tested in secret.
Two have decided to return to their home countries rather than remain in prison.
Mr Blunkett wants to extend this so prosecutors can take action against suspected British extremists even though the evidence may not be strong enough to win a conviction under existing laws.
This may mean lowering the burden of proof in such cases from "beyond reasonable doubt" to what is acceptable in civil cases, "the balance of probabilities".
Evidence in the new trials would be kept secret from the defendants to protect MI5, MI6 and GCHQ intelligence sources, Mr Blunkett said.
Speaking on a tour of the sub-continent, Mr Blunkett said: "We have to have prevention under a new category
which is to intervene before the act is committed, rather than do so by due
process after the act is committed when it's too late.
Asked if British nationals suspected of terrorism should be imprisoned on a lower burden of proof, "the balance of probabilities", he said: "Yes, I want that debate.
"It is about the threshold of evidence and the nature of those involved being accredited and trusted not to reveal the sources."
BBC security editor Frank Gardner said the measures would be "deeply unpopular", but were wanted by the government because of the difficulties of getting successful prosecutions using the likes of tip-offs and wiretaps.
He said the people currently held without charge in Belmarsh prison in London were not helping with intelligence, being charged or being deported and were therefore left in a "legal limbo".
Louise Christian, who represents Mr Abbasi, said Mr Blunkett's attitude was "enormously disappointing" for those who were fighting unlawful detention by the US.
"He is going around the world making these very extreme announcements and I don't think he's fit to be home secretary."
Senior lawyer Baroness Kennedy said the proposals were a disgrace.
"It is as if David Blunkett takes his lessons on jurisprudence from Robert
Mugabe," she told BBC Radio 4's Today programme.
"He really is a shameless authoritarian... it really is an affront to the rule of