Christopher Nuttall, the Home Office's director of research, said yesterday that an upturn in crime would place an added burden on Britain's prisons, which are already seriously overcrowded.
The warning came as the Home Office released statistics showing that courts were being increasingly tougher in sentencing offenders.
"The largest single determinant of the crime rate is the state of the economy," Mr Nuttall said. "If the economy starts to cool off, this will have an impact on recorded crime rates."
With the prison population standing at a record 65,000, Jack Straw, the Home Secretary, is anxious that the courts should make full use of alternatives to custodial sentences.
Figures released by the Home Office yesterday show that average sentences are continuing to rise. Since 1992, the average sentence length has increased from 191/2 months to 221/2 months.
Last year, 93,100 offenders were given immediate custody by the courts, an increase of 10 per cent on the previous year.
In all courts, 22.6 per cent of offenders were given immediate custody, the highest figure for at least 40 years.
The use of cautions, fines, probation orders and community sentences fell last year.
Last week, the Home Affairs select committee urged the courts to make greater use of alternatives to prison, particularly community sentences.
Senior government officials are concerned that the severity of sentencing by the courts far exceeds public demand for harsher punishments.
In recent Home Office research, 55 per cent of people underestimated the courts' use of imprisonment for burglary by at least 30 per cent. Only 8 per cent overestimated its use.
For rape, nearly 60 per cent of respondents were under the impression that fewer than two out of three offenders were sent to prison. In fact, 99 per cent of rapists over the age of 21 are immediately jailed.
"The mismatch between public perceptions about sentencing and the reality matters," said Mr Nuttall. "People's actions will be affected by the threat of punishment, and by their beliefs about the consequences.
"If they think the risk of imprisonment is much less than it really is, then the deterrent effect will be weakened."
He added: "Sentencers believe there is strong public pressure for greater toughness.
"Our research showed that the public did indeed think that the courts should be tougher but they also believed them to be much less tough than they actually were."
Mr Nuttall said that when members of the public were asked to suggest an appropriate sentence for an offender - after being given details of the offence and the person's criminal history - they invariably suggested a "significantly more lenient sentence" than the offender actually received.Reuse content