Prison sentences of less than eight weeks should no longer be imposed by the courts, the Magistrates’ Association is urging, in defiance of more radical government proposals.

In an attempt to redirect the debate on rehabilitation of offenders and prison overcrowding, the body that represents all magistrates in England and Wales has intervened to suggest that only very short sentences should be replaced.

This spring the justice secretary, David Gauke, made a clean break with traditional Conservative policy and suggested following Scotland’s initiative in adopting a presumption against prison sentences of less than six months.

Short jail terms disrupt family lives and do little to reduce reoffending, Gauke said. Instead tough community orders should be used, backed up by tagging. His proposed six-month sentence limit has not yet been out for consultation or incorporated into any parliamentary bill.

The Magistrates’ Association, which speaks on behalf of about 16,000 lay magistrates, argues that a distinction should be made between very short sentences of up to eight weeks and those of about six months.

John Bache JP, national chair of the association, said: “If current provision of robust and effective community alternatives to custody could be guaranteed in all areas, this would increase sentencer confidence. Once this is in place, the [association] would support restrictions being placed on the use of immediate custody to support the Ministry of Justice in its aims to reduce the use of short prison sentences.

“Sentencers must retain discretion to order immediate custody if existing orders have been breached and there are no appropriate alternatives, but otherwise sentences of up to eight weeks should be restricted so that they are only available in the most exceptional circumstances.”

Magistrates could in future be required to give a community order, instead of a prison sentence of less than eight weeks, apart from when an offender has breached an existing order or in exceptional circumstances, such as where the offender is only in the UK for a few weeks so could not engage with community options.

Magistrates can only impose prison sentences of up to six months for a single offence or up to a year for multiple offences. The justice secretary’s proposals would effectively take away many of their sentencing powers. Magistrates can always send cases up to the crown court if they believe a longer prison sentence is required.

The Magistrates’ Association believes its eight-week limit “could have a significant impact on reducing reoffending rates, as evidence suggests that very short prison sentences are very disruptive to the employment, accommodation and caring responsibilities of an offender, but offer limited opportunities for rehabilitation”.

Offenders given a community sentence as an alternative to custody must receive adequate support and monitoring, the association says, ensuring that breaches are dealt with promptly and appropriately.

It adds: “We call on the Ministry of Justice to ensure sentencers can be confident in alternatives to custody being available, effective and robustly managed before any proposed change in law.”

A sharp decline in the use of community sentences has been a result of trust breaking down between judges, magistrates and the probation service after privatisation, according to the Centre for Justice Innovation.