Emergency laws are to be rushed through Parliament permitting anonymous evidence in court, such as the testimony used to convict the killers of Birmingham teenagers Charlene Ellis and Letisha Shakespeare.
Harriet Harman, the leader of the Commons, set out a timetable for new legislation in a bid to end the crisis in the criminal justice system caused by a surprise legal ruling last month.
Law Lords had ruled that a man convicted of two murders in London in 2004 had not received a fair trial, because the court had heard evidence from anonymous witnesses. He can now appeal against his conviction.
Their decision paved the way for other convicted killers to appeal, including the four men convicted of murdering Charlene, aged 18, and Letisha, aged 17, in Aston in 2003.
The case was the first in which anonymous evidence was used. Since then, it has become an increasingly common weapon for police in trials where witnesses could face intimidation, such as cases involving gangs.
A £6 million murder trial at the Old Bailey collapsed days after the Law Lords ruling, and dozens of others have been put on hold.
Police believe up to 60 people convicted of serious crimes in London alone could walk free if witnesses refused to reveal their names in a retrial.
Emergency legislation is to be rushed through the Commons in just one day, next Tuesday.
Jack Straw, the Justice Secretary, pledged that criminals convicted by evidence from anonymous witnesses will not walk free. He said: “Allowing witnesses to give evidence anonymously has played a vital role in bringing the most violent criminals to justice and it must continue to do so.
“It has also been essential to act so swiftly so as not to leave a gap in the public and victims’ protection against serious crime.”
Ministers are hoping to secure cross-party support for the legislation to ensure it is not delayed.
Police have expressed dismay at the Law Lords’ decision. Detective Chief Superintendent Dave Mirfield, senior investigating officer in the Charlene and Letisha case, said last week: “Special measures are a vital tool in bringing about successful convictions, particularly in complicated investigations.”