Campaigner Sara Payne, whose daughter Sarah was murdered, has criticised the government's decision to break up the Forensic Science Service.
She said Sarah's killer, Roy Whiting, would be free without its work.
Her comments come after 33 leading forensic scientists warned the UK's justice system would take a "backward step" if the service closed.
The Home Office said it was confident the move would not adversely affect the criminal justice system.
It has decided to break up the service, which makes an operating loss of £2m per month.
Ms Payne, a chief advocate for the Phoenix Foundation, which campaigns on child abuse issues, said the decision should not be guided by money.
She said: "As a victims' advocate, I can tell you that 90% of most current sex offender cases rely on forensic services to prove their cases.
"Over the years we've worked with thousands of victims who wouldn't have got justice if it were not for the highly-regarded FSS.
"Roy Whiting, and countless other offenders I can think of, would not be in jail if it were not for the FSS."
She accused the government of "betraying the British public and cheating them out of the justice they not only deserve, but agree to pay for".
"Why has there been no public consultation? Why doesn't the government ask the public if they mind paying £2m a month to get something this important right?," she added.
Ms Payne told the BBC News Channel she was concerned that its break-up could result in a "postcode lottery" for victims of crime and that it could be the "thin end of the wedge", leading to a privatised judicial system.
She added: "Justice shouldn't and doesn't come at a price. It shouldn't be about who can do it cheaper, it should be about who can do it better."
The warning from forensic scientists came in a letter to the Times, which said the decision could make the UK lose its position as the world leader in crime-scene investigations.
It was signed by international scientists including the pioneer of DNA fingerprinting, Professor Sir Alec Jeffreys.
International Society for Forensic Genetics president, Professor Niels Morling, who co-ordinated the letter, said there was global support to save the Forensic Science Service (FSS).
He said: "So many of us have benefited from the research, development and education offered by the FSS - a worldwide network of scientists is grateful to the FSS and to British society.
"Our plea to the British government is: 'Please consider what you will do next - ask where [you] will be in five or 10 years' time if this goes ahead?'
The FSS has been involved in a number of high-profile cases, including those of Soham murderer Ian Huntley and Suffolk Strangler Steve Wright.
The Home Office says the FSS is expected to be wound up by March 2012, with the loss of about 1,600 jobs.
Crime reduction minister James Brokenshire said: "The Forensic Science Service is making significant and unsustainable operating losses and it is vital we take action to remedy this now.
"We believe in a competitive market, overseen by the Forensic Science Regulator to ensure quality standards are maintained. Research will continue to provide innovation in this area to help solve crimes."
The FSS has two offices in Birmingham and sites in Chepstow, Chorley, London, Huntingdon and Wetherby.