Liberal Democrat leader Charles Kennedy said history showed that rushed law changes supported by all UK parties had tended to be bad legislation.
He added that ID cards had failed to stop terrorism in other countries - such as France, Spain and Italy - where they were already in place.
The UK government is considering making identity cards compulsory as part of a crackdown on terrorism.
Home Secretary David Blunkett says he will not be rushed into making a "snap announcement" on cards or any other anti-terror measures.
He said: "I'm giving it a fairly high priority in terms of the discussions and the consideration behind the scenes.
"There are much broader issues about entitlement and citizenship and not merely security in terms of some form of identity card which we are looking at very seriously indeed."
He also maintained that improvements in electronic thumb or fingerprint technology or even "iris-prints" meant the threat of forgery would not make the system redundant.
'Rushed legislation'
But Lib Dem leader Charles Kennedy said: "Rushed legislation, particularly if it's got all party agreement, history teaches, is usually bad legislation."
Mr Blunkett maintained there was no need to recall Parliament in the next fortnight to debate new laws as they would take time to draft.
"Whatever we do will take time to put through Parliament even with emergency measures."
He said drafting and discussion would take time as was appropriate in a democracy.
But the home secretary admitted the "balance" between the Human Rights Act and anti-terror provisions may need to change.
Fighting terrorism
He said: "There will be tensions between the ECHR [European Court of Human Rights] and the Human Rights Act and the necessary protection that we seek.
"It is possible that we will have to change the balance."
The Conservatives have said they will support whatever steps are needed to fight terrorism.
Shadow foreign secretary Michael Ancram said the country always had to be careful about curtailing freedoms.
But he said the party would look at any proposal for identity cards or any other measure to fight terrorism.
Author and terrorism expert Michael Yardley said: "It is unfortunate that there are some people who will use the insecurity that is apparent at present to introduce draconian security measures for which there has long been support in certain quarters - but for which there has been public resistance."
Liberal Democrat foreign affairs spokesman Menzies Campbell, on BBC Radio 4's Today programme, questioned whether identity cards would be effective.
"Supposing you and I and everyone else in the United Kingdom had had compulsory identification cards on September 10 - are we both satisfied that there would have been no atrocities of the kind that took place in Washington and New York?
"If, however, a case could be made for identification cards which demonstrates that they will make a substantial contribution towards seeking out and preventing the sort of terrorist activity which took place in the United States here in the United Kingdom, then I will most certainly consider that case on its merits."