On this week's Politics Show, the Shadow Foreign Secretary, William Hague, denied the Conservatives were in danger of appearing to say that they knew better than the head of MI5 and the Commissioner of the Metropolitan Police.
Mr Hague said: "I don't think that Parliament can ever just take the orders as it were - take the instructions - of people in the security services.
"You do have to weigh that up. But Parliament in the end has to make the decision.
"So as I say, if the government comes up with an argument that gives instances and cases in which a longer period of detention has been necessary, that would make a big difference to how Conservatives think about this.
"But we are not just going to give a blank cheque to the government to do anything it wants."
Mr Hague was also questioned by Jon Sopel about the Conservatives' policy towards Iraq.
"Certainly there should be a reassessment going on," Mr Hague said, "because clearly Iraq at the moment, which could still tip either way, is tipping in the wrong direction.
"It's very important there is heavy British involvement in that reassessment, that it's not just an American process and certainly there are things that need doing better such as the tackling of corruption in Iraq, of the reconstruction in Iraq and of course we have to look at whether we can bring other countries in to help dealing with it."
Join Jon Sopel and guests for the Politics Show on Sunday 19 November 2006 at 12:00 GMT on BBC One.
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