Poor conditions in court cells and prison vans are contributing to suicide and self-inflicted injuries among prisoners, a prison reform charity has warned.

Publishing its latest report on the prison system, the Howard League for Penal Reform said cold and dirty court cells, a lack of welfare support and long hours spent in claustrophobic vehicles were contributing to the problems among prisoners.

The Howard League called for more action to provide better care for prisoners.

Among its demands were that the Prison Service should take responsibility for conditions in court cells to ensure consistent standards and that an independent review of the privatised prisoner escort services should look for ways to end the practice of housing prisoners in police stations overnight.

The Howard League also said "link workers" should be employed to ensure prisoners' welfare at larger courts and that there should be better information about prison for people held in court cells.

Tim Colbourne, the author of the report, said there had been 376 incidents of self-harm in court cells and prison escort vehicles in the last year. There have also been eight suicides in court cells since the escorting service was contracted out.

"This is likely to be the tip of the iceberg, because men, women and children who are traumatised by their experiences at court carry their stress and anxiety with them into prison. Twenty-eight per cent of suicides take place within a week of reception to prison.

"People held in court cells are predominantly unconvicted or unsentenced. They should be treated at all times with humanity and respect. They should not be kept in holding cells or prison vans for prolonged periods, and must be given information about what is going to happen to them," said Colbourne.