Former politician turned Christian writer and speaker Jonathan Aitken has challenged his listeners to "Go back and ask your own church - does your church do anything in the way of prison ministry or after-care for prisoners? And if not, why not?"

Speaking at this year's Keswick Convention, Mr Aitken voiced concern over re-offending statistics which show that seven out of every 10 released prisoners are back in jail within two years, while nine in 10 prisoners from young offenders institutions are back behind bars within two years.

"That is a terrifying failure rate and one that society as a whole should be thinking about, not just those responsible for the prison service," he said. "There is something wrong with the system here ... we are bad at one vital element in the prison system - rehabilitation."

Mr Aitken went on to highlight the high rate of illiteracy among prisoners, with one third of all inmates having no reading or writing skills at all.

"Launching a real attack on prison literacy would be a step towards rehabilitation," he said, adding that skills training would also go some way to keep released prisoners from re-offending.

Turning to the drugs problems in British jails, Mr Aitken said that proper rehabilitation centres inside prisons were crucial in efforts to break re-offending caused by drug abuse.

Mr Aitken suggested mentoring, which has been hugely successful in the US in cutting re-offending rates. "If you look around the world, you will find there is more and more success in reducing re-offending rates in post-release mentoring. It is almost always Christian post-release mentoring because often - not exclusively - it is the Christian churches that volunteer for this."

He pointed to the Inner Change ministry led by Chuck Colson in the US, which runs Christian mentoring with prisoners in jail and in the months following their release. According to Mr Aitken, the repeat offending rate among those on the scheme is now just seven to eight per cent, in comparison to the national average in the US of 65 per cent.

"There are areas of hope and we shouldn't be satisfied with the repeat offending rate where it is now. We should say that we can do more about this," he said.