Mr Grieve: Health and safety rules are holding officers back
Measures to help the public and police tackle criminals and end the "walk on by society" have been outlined by shadow home secretary Dominic Grieve.
He told the Conservative Party conference that too many people making "genuine attempts to prevent crime" had been arrested or prosecuted.
"It's our duty to help not hinder active citizens," he said.
But the government said it was already boosting the police in protecting the public against crime and terrorism.
Mr Grieve's comments came after banker Frank McGarahan died following an attack in Norwich.
The 45-year-old intervened when he saw two other people being assaulted in the early hours of Sunday morning, but was himself set upon, suffering fatal head injuries. Police have launched a murder inquiry.
The Conservatives want to make it easier for the public to stop anti-social behaviour and crime by reducing the risk that "have-a-go heroes" will find themselves being prosecuted.
They claim there is evidence that the police and prosecutors are too ready to accept allegations made by criminals against people who try to apprehend them.
They say they will amend the code for crown prosecutors and the Police and Criminal Evidence code of practice to reduce the chances of someone acting in good faith being taken to court.
Mr Grieve pledged to "take on the health and safety culture" and the legislation which "is holding officers back and making them more risk averse".
"It is dangerous. It undermines public confidence. And we're going to change it," he said.
The Conservatives point to examples like the case of 10-year-old Jordan Lyon, who drowned in May 2007 saving his younger sister.
Two community support officers were at the scene but did not get into the water because they had not received the appropriate training.
The Conservatives want to amend Section 2 of the Health and Safety at Work Act 1974 to ensure that protecting the public from risk is given priority over the risk to officers.
They also want to amend Sections 3 and 7 of the act to ensure it is not used to target the police when high-pressure operations, like the shooting of Jean Charles de Menezes, go wrong.
The Tories say other, more appropriate measures, should be used - and say that the health and safety culture is making police too risk-averse.
Mr Grieve also paid tribute to his predecessor, David Davis, whose resigned his seat in protest at what he called the government's "erosion" of fundamental British freedoms.
He was re-elected as an MP, but replaced by Mr Grieve on the Conservative front bench.
"We're winning the arguments on freedom and David Davis deserves the credit for his stand," he said.
But the government said its was already working on the issues the Conservatives had raised, including changes to the law, so people using "reasonable force" to protect themselves could have "greater confidence" they would not be prosecuted.
Home Office Minister Tony McNulty said: "The lives of police officers and PCSOs [police community support officers] are as important as those of the people they serve, and this government will back the police service in the day to-day operational decisions they make in protecting the public against crime and terrorism.
"And we will ensure that the criminal justice system is firmly weighted in favour of the victim, not the criminal."