On Wednesday Full Fact investigated the Shadow Health Secretary's claim that 70 per cent of prisoners have two or more mental health conditions.

The claim stemmed from figures compiled by the Office for National Statistics in 1998, which calculated how many prisoners suffered from each of five psychiatric disorders (psychosis, neurosis, personality disorder, hazardous drinking and drug dependence).

At the time, Full Fact noted that the Prison Reform Trust made a similar claim that 75 per cent of prisoners suffered from "mental health problems combined with alcohol or drug misuse" in their December 2011 issue of the Bromley Briefings.

However, the Trust referred to a report by the Offender Health Research Network which appeared to only claim 71 per cent suffered from "a current SMI (Serious Mental Illness), substance misuse problem or both". Full Fact queried whether this was the figure to which the trust intended to refer.

The Prison Reform Trust have since been in touch to correct their reference. Their claim was originally taken from a study by the Social Exclusion Taskforce, which in turn referenced the OHRN report.

The Taskforce claim that "the national evaluation of prison mental health in-reach services in August 2008 found that 75% of the sample had a dual diagnosis (co-existing severe and enduring mental illness and drinking and/or drug problem)", although this is not what the OHRN report suggests.

The Prison Reform Trust have confirmed that the figure will be amended or removed from the next edition of the Bromley Briefings.