Dr Stephen Moston, who carried out a study for the Royal Commission on Criminal Justice in the Metropolitan, Bedfordshire and Cumbria force areas, found about 8 per cent of police admitted carrying tape recorders, often against force guidelines.
Dr Moston said he was first told of the practice in Cumbria. 'It particularly applies to traffic officers who, when they stop a car, turn on their tape recorders in their pockets to prevent subsequent allegations that they had said something untoward.'
Dr Moston was speaking before a conference on police questioning at Church House, Westminster, London.
Police must stick 'rigidly' to national guidelines when questioning suspects, according to an Inspectorate of Constabulary report into policing in east London that highlights criticism of the quality of tape-recorded interviews.
The report says the criticism was brought to the Inspectorate's attention by the Chief Crown Prosecutor, who said that there were still many examples when the quality of tape-recorded interview was 'less than desirable' and the subsequent written records 'inadequate'.Reuse content