The Government's claims that electronic bail could reduce the prison population have been proved wrong, National says.
"The scheme was designed to save prison beds but it's failing to deliver on that," National justice and corrections spokesman Simon Power said.
The scheme aimed to give electronic bail topeople who were likely to be found not guilty or get a non-custodial sentence, rather than remand them in jail.
"The problem is that in the first 10 months of the scheme they have found only 56 defendants suitable for electronic bail. And of the 19 who had their cases concluded by early July, 11 were convicted and sentenced to prison."
That meant the difference - eight people - who had been remanded on bail never took up a prison bed, Mr Power said.
A Justice Ministry Cabinet paper he released said it was hoped the scheme would mean 120 new prison beds would not need to be created.
The Cabinet paper said: "To have any real effect on the prison population, any changes to bail must prevent remand in custody of defendants who will not subsequently be found guilty or receive non-custodial sentences."
Mr Power said it was a concern that people who were on electronic bail were then sentenced to jail, which raised questions about whether they should have been remanded in custody.
In June Mr Power revealed 40 of the 46 people allowed electronic bail in its first eight months had a history of offending while remanded at large.
Of those, 20 faced charges for violence-related offences.
Since September last year courts have had the option of releasing alleged offenders with electronic monitoring as a condition of bail.
Under the controversial scheme bail defendants wear a monitored electronic bracelet, which sets off an alarm if they leave home.
