Labour got the balance wrong between national security and civil liberties when in power, Ed Balls has said.
The shadow home secretary told BBC One's Andrew Marr Show dealing with the issues was "really hard" at a time of heightened terror threats.
The 28-day limit on holding terrorism suspects before they are charged is being reviewed by the government.
Mr Balls said Labour may back cutting it to 14 days and said moves in 2005 to make it 90 days were a "step too far".
Home Secretary Theresa May announced a review of counter-terror legislation in June, when she said her view was that the limit should be 14 days, which the Liberal Democrats also support.
Mr Balls spoke to the BBC after telling the Sunday Telegraph Labour's reputation had suffered from its attempts to raise pre-charge detention limits for terrorism suspects to 90, then to 42 days.
The policy was opposed by civil liberties campaigners and, in 2005, Tony Blair's attempt to make the limit 90 days resulted in his first Commons defeat as prime minister - 49 Labour MPs were among those voting against it.
'Step too far'
Asked whether Labour had got the balance wrong on civil liberties issues, Mr Balls told the BBC: "Yes. it was really hard. We had these massive terror threats, we had the plots.
"I think successive home secretaries did a brilliant job to make sure we acted and got the resources in and updated our legislation.
"But in retrospect I think everybody would say 90 days was a step too far for pre-charge detention".
He said they should await the findings of the review but "if we can get a consensus on counter terrorism then we should" and any pre-charge detention "should be at the minimum amount necessary".
"People thought 28 days might be needed, in fact in the last three years it's not gone beyond 14 days so I've said today that if we can get it down to 14 days and if the police and security experts say that is consistent with the terror threat, then obviously we should do that."
But he added MPs should not have to come back and debate new emergency legislation if 14 days was not enough: "There is one suggestion that after 14 days we might bail people until 28 days, so you can let them out but have restrictions on their movement. That's something we should look at."
"But definitely I think there is need for a change."
'People want CCTV'
The review, overseen by former director of public prosecutions Lord Macdonald, is also considering control orders - introduced under 2005 anti-terrorism legislation, which place terrorist suspects under close supervision some compare to house arrest.
Mr Balls told the BBC that if police and security services could persuade the home secretary that alternatives such as travel restrictions and increased surveillance could work, Labour should support it.
But he added it was a tough issue: "The jury's still out on this one. We don't yet know if an alternative to control orders can work".
However, he said the DNA database and CCTV cameras had resulted in convictions and people wanted more CCTV "because they want to feel safe".
Mr Balls's comments about pre-charge detention were welcomed by backbench Labour MP David Winnick, who said: "We need to restore our position on civil liberties.
"This step is very much in the right direction of making it clear that while everyone recognises the continuing threat of terrorism, 14 days should be the maximum for holding someone without charge."
Civil liberties campaign group Big Brother Watch said the government should now debate whether to go lower than 14 days.
Director Alex Deane said: "This is good news. It means that there is simply no excuse for the government to keep the limit at 28 days - even the authoritarian Labour Party which introduced 28 detention now agrees that it's wrong."
Mr Balls also attacked spending cuts to the police as "hugely risky and very dangerous for crime in our society".
Labour says its research suggests almost every police force in England and Wales has stopped recruiting officers because of spending cuts - so officers who retire or resign are not being replaced.
Mr Balls said plans for 20% spending cuts were behind the recruitment freeze: "This is an early sign that the spending review will hit frontline policing hard."
But for the government, policing minister Nick Herbert told the BBC that - because police forces also get money from local councils - the cuts were on average "only 14% in real terms".
He added that only a "small proportion" of police officers were visible to the public at any one time: "I think that's partly because of a huge growth of bureaucracy that we saw under the last government - we've got to change that.
"So it's not just about the overall numbers of police officers, it's about what they're doing."