A review is being launched into the law in England and Wales protecting those who intervene in criminal situations.
Justice Secretary Jack Straw, who has been a "have-a-go hero" four times, said he wanted to clarify "that the law is on the side of the citizen".
He said self-defence laws work "much better than most people think, but not as well as it could or should".
The Conservatives said they had long called for a change in self-defence laws and called this "long overdue".
Mr Straw said he wants to reassure victims or witnesses that they can use reasonable force to stop and detain offenders.
He made the announcement as Labour's annual conference in Bournemouth drew to a close with the party's traditional send-off, delivered by deputy leader Harriet Harman.
Mr Straw said he knew "from personal experience that you have all of a millisecond to make the judgement about whether to intervene" in a crime.
"The justice system must not only work on the side of people who do the right thing as good citizens but also be seen to work on their side."
Of the four times when Mr Straw has intervened to stop criminals, he managed to detain the offender on three occasions.
In 1980 he overheard a burglar breaking into a members club in his Blackburn constituency, chased him down the street and detained him until police arrived.
In the mid 1980s at Oval Tube station in south London he came across an 11-year-old boy who had just been robbed by a man and detained the offender.
He chased a man who had attacked a woman at the same underground station in the early 1990s, but did not catch him.
Then in 1996 he chased a man who had robbed a member of the public and detained the suspect until police arrived.
"I was presented, just by chance, with being a witness to criminal behaviour and thought I should intervene," Mr Straw told BBC Radio 4's Today programme.
"You haven't got time in that situation to wonder where does the balance lie - what constitutes reasonable force."
He went on: "No-one knows whether you're going to intervene until it happens.
"Those that do intervene in this situation face the anxiety that they'll be the subject of a police investigation.
"Too many unnecessary police investigations take place. I want to make the law clearer."
Mr Straw wants people to be aware that the Criminal Law Act 1967 allows them to use reasonable force to apprehend suspects, but was not advocating recklessness, his spokesman said.
Home secretary's speech
Shadow Secretary for Justice Nick Herbert said that Mr Straw and Labour MPs had repeatedly rejected Conservative calls for the law to be changed to allow people to defend their homes against burglars.
He added: "The last time the Government cynically signalled a change on this they reneged just months later. People will rightly question the motive and substance of this latest review."
Liberal Democrat home affairs spokesman, Nick Clegg, said the law did not need to be changed as it was "already very, very clear" that "proportionate, reasonable force" could be used.
"My concern, frankly, is the government appears to be a bit confused," he told BBC Radio Five Live.
"On the one hand, Straw seems to be saying the law is working better than people think.
"On the other hand he seems to be stoking up public fear, if you like, by saying 'I'm going to review it', but not really saying in what way it's going to be reviewed."
The Association of Chief Police Officers, the Crown Prosecution Service, judges and other government ministers are expected to be consulted during the review.
Meanwhile Home Secretary Jacqui Smith's speech covered, among other issues, Labour's commitment to give local people more information about the performance of local police, and tougher checks on people travelling to the UK.
She rejected Conservative claims there was "anarchy in the UK" and said it was irresponsible to stoke up people's fear of crime.
But shadow home secretary David Davis later rejected that suggestion.
He said: "The Home Secretary is in denial about the problems we face, which makes her part of the problem. No-one believes violent crime is down and her own department says it has doubled."