Opposition parties and pressure groups said that the escape of the pair, reportedly a Briton of Pakistani descent and an Iraqi, highlighted that the control orders to which they were subject were dangerous and unfair.
Control orders are a loose kind of house arrest which usually compel suspects to report regularly to police and place them under a curfew, although critics say suspects should instead be charged and face a trial.
But Home Office minister Tony McNulty hinted on Monday that the government may go in a different direction and diverge from the European Convention on Human Rights to tighten up the regime using existing legislation.
"We've got scope... to look at derogating orders that actually step away from the European Convention on Human Rights. That remains an option and we keep these things under review," he told BBC television.
The Home Office has not made public any details of the escapes, but the BBC reported on its website that one of the fugitives was a British man of Pakistani descent suspected of wanting to go to Iraq and fight against the United States and British-led coalition there.
He is 25 and escaped from the mental health unit of a hospital in south-west London in the last few weeks, Britain's Press Association (PA) reported.
The other man is Iraqi and is thought to have been missing for some months, the BBC online said.
Home affairs spokesman for the main opposition Conservative party David Davis called for a review into the situation, while his Liberal Democrat counterpart Nick Clegg said that the government should be getting more control order suspects into court.
"As we have always made clear, the danger of control orders is that they short-circuit due process and keep suspects in a state of limbo," Clegg said.
Shami Chakrabarti, director of civil liberties campaign group Liberty, said the two escapes confirmed that control orders were "unsafe and fundamentally unfair".
"If someone is truly a dangerous terror suspect, why would you leave them at large? "On the other hand, it is completely cruel and unfair to label someone a terrorist and to subject them to a range of punishments for years on end without ever charging them or putting them on trial," she said.
Prime Minister Tony Blair was likely to face questions from the media over the issue at his monthly press conference at noon (1100 GMT).
Control orders were introduced last year to replace emergency laws brought in after the September 11 2001 attacks in the United States which allowed the government to lock up foreign nationals suspected of involvement in international terrorism without charge or trial.
When Britain's upper parliamentary chamber, the House of Lords, ruled those measures illegal, the government brought in control orders.
Human rights legislation prevented the men from being deported because they faced being sent to countries where they could be tortured or treated badly.
In June, a senior judge quashed control orders made against six men, saying they were incompatible with article five of the European Convention on Human Rights, but the government has appealed this ruling.

Copyright AFP (Agence France-Presse), 2006