The law surrounding gang murder cases is now so complex that juries "may find it impossible to understand how to reach the right verdict", MPs have said.
A new law is needed "to ensure justice for both victims and defendants" and end the high number of appeals, the dommons justice select committee said.
But prosecutors should urgently be given new guidance in so-called joint enterprise cases, particularly those involving gang-related killings, to help clarify the situation before a new law can be brought in, the MPs said.
The legal principle of joint enterprise means that anyone who agrees to commit a crime with another person becomes liable for everything that person does during the offence.
In December, five teenagers were given long sentences of detention for killing a 15-year-old boy who was stabbed to death as he arrived at school.
Speaking after the case, Detective Chief Inspector John McFarlane said: "The law on joint enterprise is clear and unforgiving - if you are with the knife man in a murder case you too could be found guilty and sent to prison."
Sir Alan Beith, the committee's chairman, said: "This area of law is vital to ensuring the prosecution and conviction of criminals involved in gang-related violence in particular, but is now so complex that juries may find it impossible to understand how to reach the right verdict."
He said that while joint enterprise could help deter young people from becoming involved in gangs, "confusion over the law and how it works can put vital witnesses in fear of coming forward, allowing the real criminals to escape justice".
"It is also important to ensure that young people are not unnecessarily brought into the criminal justice system when they are on the edge of gang-related activity," Sir Alan said.
He called for action to be taken immediately, saying it "should not wait for a general review of the law of homicide which few governments would be willing to undertake".
The Director of Public Prosecutions, Keir Starmer QC has agreed to produce the guidelines called for by MPs.
"Having studied the report and considered its content I have decided that the CPS will now produce guidance on the approach we will take to cases of joint enterprise, including guidance on the proper threshold at which association potentially becomes evidence of criminality," he said.
"This exercise will be done through consultation, with interested parties, on draft guidance in due course, and as with all CPS guidance it will be kept under review.
"The CPS will also now consult with the Ministry of Justice on the best way forward for collating statistics around cases involving joint enterprise."