Lord Falconer has tried to persuade peers not to ruin his prevention of terrorism bill,insisting that judges would examine the merits of a home secretary's decision to impose control orders on suspects.

The constitutional affairs secretary said judges would be able to look at the facts surrounding the case.

"Someone subject to a control order such as a curfew would be able to go to the courts in a matter of days and say this is disproportionate," he said.

"The courts would be able to weigh whether this is [so]."

Critics of the legislation claim judges will have little option but to rubber stamp a decision to issue orders short of house arrest, such as curfew and tagging as long as the home secretary had acted within the rules.

Ken Macdonald, the director of public prosecutions, has warned: "We are at a point where we could make reforms we could live to regret."

Meanwhile, the Times reports the Conservatives have vowed to ensure the control orders will become law next week.

Senior Tories insisted that, although they disagree with much of the Bill, they are determined not to be painted as soft on terror by Labour in the election campaign.