Lord Falconer has dismissed suggestions there is a split between the judiciary and the government when it comes to applying anti-terrorism laws.
The lord chancellor denies terror law split
On Wednesday Tony Blair said he expected judges to uphold any new laws.
But ex-master of the rolls Lord Donaldson said: "It is the judges whose job it is to ensure the government of the day does not exceed its powers."
The lord chancellor said all parties agreed on the need to change the law in the wake of the London bombings.
Lord Donaldson told BBC Radio 4's Today it was the job of Parliament to perform the balancing act between ensuring civil liberties and tackling terrorism.
But on the same programme Lord Falconer said: "Nobody would dispute a change in the facts means you need a change in the law - and that's where we are.
"But the idea that this leads to a conflict is wrong. All those bits of the state and the executive complement each other.
"Of course from time to time the judges are going to say this is where the boundary is and you can't further than that."
He added that there was no freedom for people if they did not feel secure.
On Wednesday Prime Minister Tony Blair's wife Cherie, a top QC, warned against responding to terror "in a way that undermines commitment to our most deeply held values and convictions which cheapens our right to call ourselves a civilised nation".
She told a conference of 1,000 lawyers, civil servants and diplomats in Malaysia, that judges made rulings in a way that taught citizens and government about the "ethical responsibilities" of participating in a true democracy committed to "universal human rights standards".
Mrs Blair added: "Sometimes democracy must fight back with one hand tied behind its back. None the less it has the upper hand."
Later on Wednesday Mr Blair told reporters that he agreed that there was a balance to be struck between people's freedom and their security.