BBC News has reported that more than 118,000 offenders have taken part in untested rehabilitation programmes.
Sex offenders and domestic abusers are among the offenders in rehabilitation measures which haven't been subject to any "outcome evaluation".
The charity Transform Justice, which compiled the data, said that it had asked for the evidence that the programmes delivered in prisons and for those on probation worked and was surprised when none was forthcoming.
In response, the British Ministry of Justice said that although it aimed to conduct evaluations to an "academic standard" it could take years to develop a "robust data sample".
No outcome evaluation
Government figures supplied to Transform Justice reveal that 25 offender behaviour programmes, run either in prisons or through the probation services, have not had any outcome evaluation.
Between 2010 and 2018, 16,434 prisoners in England and Wales began non-evaluated courses and 101,662 offenders serving community sentences started such programmes between 2009/10 and 2016/17.
Some of the programmes involves cognitive-behavioural intervention to reduce violence, as well as goal-setting skills training.
More than 20,000 sex offenders did courses which have not been fully evaluated.
Peter Neyroud of the Department said he was "concerned" about the findings.
"You would have expected that every significant programme that the Ministry of Justice is funding and recommending out for delivery would have a clear basis in evidence, and would be tracked to make sure that it's actually matching the outcomes you'd expect – and I can't see from the evidence I've seen here that this is happening," he told BBC News.
In March 2017, the Department stopped its main sex offender treatment scheme after research found that those completing the programme were slightly more likely to offend than a control group.