Peter Morris, whose sister Claire was murdered by Malcolm Webster, says the proposed Victims and Witnesses Bill lacks empathy and needs to be completely re-written.
Mr Morris, who has campaigned for victims' rights ever since Webster was jailed for a minimum of 30 years in 2011, claims the bill is allowing the Government to indulge in the "worst sort of politics – the politics of appearing to do something and taking credit when they don't deserve it".
His views have been backed by Trina Stewart, whose brother Andrew Oates was killed by his partner Sharon Hollinsworth, despite the Government saying it consulted with victim support groups while developing the bill.
Mr Morris said: "In my two years of campaigning, I have rarely felt more disappointment than I did when I saw the bill.
"To say that this legislation as it stands will make any significant difference to victims' lives is just not true. To say that this legislation is radical is not true and to say that this now puts victims at the heart of the justice system is also not true."
One of the key proposals in the bill is the Victims' Surcharge, which will see offenders who receive a fine forced to pay an additional fee from £20 upwards depending on the severity of their crime.
The sum will be paid into a Victims' Surcharge Fund, which will be managed and distributed by Victim Support Scotland.
However, Mr Morris feels automatic compensation for victims would be a more effective way of ensuring the needs of those affected by crime are met.
He said: "In its current format, the Victims' Surcharge is nothing more than an appeasement. The direct victims of a particular crime will not receive compensation from their offender, the money will go to the Government and then be passed on to charities to disseminate as is their want. Is this really restorative justice?"
Mr Morris suggests the bill should include the creation of a victims' commissioner who would fight for victims' rights and the introduction of a "case companion" – a dedicated person who would provide one point of contact for victims throughout criminal proceedings.
The campaigner added: "It would be churlish to oppose a bill that attempts to create some improvements for victims, but I feel that as it stands, victims all over Scotland will feel nothing but a sense of disappointment at a missed opportunity to make some real improvements."
Ms Stewart, whose brother was killed by Hollinsworth in 2010, claims her family was let down by the lack of support they received and believes the measures outlined in the new bill, which was introduced to Parliament last month, would have made no real difference.
The 58-year-old nurse said: "Following the sentencing in the case, we were told to go outside for a statement to be read to the press and then go back into the court, but when we tried to get back in the court was locked.
"We were left out on the street with our world turned completely upside down and we've never been the same since. Our lives will never be the same again. The Government needs to listen more to people like us and try to understand what it's like."
Ms Stewart would like to see consideration given to ensuring sentences are passed in the same court where the trial was heard to ensure victims are familiar with the surroundings and staff.
She also suggests the Government introduce measures to prevent serious offenders returning to live in areas where victims or their relatives are living.
A Government spokeswoman said: "The measures contained in the bill will make important improvements to the criminal justice system, and improve the support available to victims and witnesses."
She added that the Victims' Surcharge Fund would go to individual victims and that the Victim Information and Advice service in Crown Office already provides a main point of contact for victims in serious cases.