Only one in 25 magistrates in England and Wales is aged under 40 - and urgent action is needed to address "serious" recruitment problems, a Commons report has warned.
MPs pointed to figures showing that more than eight in 10 (86%) JPs are aged 50 and over - and well over half (57%) are within 10 years of the retiring age of 70 - while the number of serving magistrates has almost halved in a decade.
The Commons Justice Committee also called for steps to increase diversity in the magistracy.
Statistics for 2016 show that 53% of magistrates are female, and 89% are white. While the latter figure is comparable to the proportion of overall population that is white, the report noted that many benches have no, or very few, black, Asian and minority ethnic (BAME) magistrates - and only 4% of JPs declared themselves to be disabled.
MPs said they recognise the valuable expertise of many older magistrates - and urged the Ministry of Justice to undertake a "workforce planning exercise" at the earliest possible opportunity.
The committee added that rebalancing the age profile is unlikely to happen unless more is done to overcome the barriers facing employed magistrates, and recommended that a "kitemark" scheme be created to recognise and reward supportive employers.
The report concluded that the magistracy faces a range of unresolved issues relating to its role and workload, together with "serious problems" with recruitment and training.
Conservative MP Bob Neill, chairman of the committee, said: " It is unfortunate that the Government's evident goodwill towards the magistracy has not yet been translated into any meaningful strategy for supporting and developing it within a changing criminal justice system.
"This needs to be addressed as a matter of urgency".
Magistrates, who are unpaid volunteers, deal with more than 90% of criminal cases - as well as a substantial proportion of non-criminal work including family law cases, according to the report.
It said the number of magistrates has fallen significantly over the past decade - the current total of 17,552 compares to around 30,000 in 2006.
Elsewhere the committee said:
:: There is sufficient evidence of low morale within the magistracy to cause concern
:: It expressed support for increasing magistrates' sentencing powers to 12 months' custody - from the current level of six months for a single offence
:: It called on the MoJ to ensure that at least 90% of users can reach the nearest magistrates' court venue by public transport within one hour
A Ministry of Justice spokeswoman said: "We welcome this report and will consider its recommendations carefully."
Chris Brace, chief executive of the Magistrates Association, said: " We're very pleased that MPs on the Committee have accepted our case for 12 months sentencing jurisdiction for magistrates.
"We hope that Government will now embrace this too by enacting dormant legislation to make it happen.
"Once in place, it will allow cases to be retained in the magistrates' courts, speeding up justice for all court-users - especially victims.
"It will also ensure magistrates can pass proportionate sentences at the right level. Government should seize this opportunity to demonstrate trust in England Wales' 17,000 magistrates, who deal with over 90% of all criminal cases."