Earlier today Gordon Brown's former special advisor wrote a terrific advice blog for David Cameron. In it he recommended against doing exactly what the prime minister has gone out and done today with his criminal justice announcement.

If this were the Great British Bake Off Mary Barry would be making that disapproving face at this half-baked policy.

David Cameron, in an attempt to 'get a grip' - as party grandees keep ordering from the front pages - has made the easiest announcement possible, he's going to "get tough" on prison sentencing.

So far so standard for Blair-lite, but he has also promised a "rehabilitation revolution". Well if he wants one of those then how about being bold and original: stop incarcerating women.

Fair and effective sentencing of criminals is an issue all governments struggle to deal with. Simply incarcerating people in Victorian prisons has been proved time and again to be a flawed approach especially for women.

On the 2nd December 2011 the UK prison population reached a record high of 88,179 prisoners. Of these how many do you think are women prisoners, maybe 10,000 or 20,000, or even 30,000?

No, the actual number is not even close to being five figures; it is in fact roughly 4,200. That's just 4.8% of the prison population. Over the past decade the number of female prisoners has increased by just 12%, a much lower rate than that of male prisoners which is approximately 30%.

The vast majority of these women are in prison for non-violent offences and have never been a danger to the public. Yet they are locked away at a cost of £50,296 per year. That's more than students pay for three years at university and more than double the average UK salary for women.

As Baroness Helena Kennedy wrote in Eve Was Framed, her excellent expose of the failings of the criminal justice system, for the majority of incarcerated women who have been failed by society, "prison is the end of a road paved with deprivation, disadvantage, abuse, discrimination and multiple social problems."

For example according to Home Office statistics up to 80% of women in prison in the UK have diagnosable mental health problems, with 66% having symptoms of neurotic disorders. Up to 50% report of having experienced physical, emotional or sexual abuse in their lives.

The purpose of prison is surely to rehabilitate offenders and in turn make society safer however prison undeniably fails to do this. Women are also four times more likely to self-harm in prison and their suicide rate is significantly higher.

If women's prisons were closed statistical evidence has proven that the vast majority of the female prison population would be of no danger to the public and would make a great saving to the public purse. There is of course a very small minority of violent offenders who would still require custodial sentences but the sentencing of non-violent vulnerable women, already excluded from much of society, to imprisonment only serves to push them further out of society compounding their exclusion and making reintegration even harder.

There is no evidence that prison works in terms of reducing the overall crime rate and 64.3% of women released from British prisons in 2004 were reconvicted within two years of release. While overall men and women commit all the same kinds of crime albeit at differing rates, of the sentenced female prison populations the majority are apprehended for property crime and theft; non-violent offences which have been attributed to the 'feminism of poverty' thesis which put simply is a high proportion of female offenders stealing in order to put food on the table for their children.

UK and prisons have been overcrowded every year since 1994. Community prisons, curfewed tagging and alternative sentences are what is really needed and the relatively small female prison population is an ideal test group for these.

For the fairer sex, prison isn't fair and if successful these schemes could be used to reduce the male prison population and reduce the cost of the penal system for a government desperate to cut the deficit. Similar trends for female prisoners have been found around the world however for governments, always keen to look tough on crime the idea of ending incarceration for women is extremely difficult politically despite the widespread unspoken belief that is does not work.