Magistrates should be able to jail offenders for up to a year, the lord chief justice has said.
Lord Thomas of Cwmgiedd said that it was a "good time" to grapple with the issue because it was unlikely to cause problems with increased prison numbers.
"We do have a serious problem with those sentenced long-term," he said. "But there is not a problem with that part [short-term prisoners] of the prison population." Lord Thomas was speaking as he formally opened the new premises of the Magistrates' Association in Vauxhall, south London, last week.
Magistrates can currently hand out sentences up to six months in length. Doubling the limit would mean more than 10,000 cases being tried by magistrates rather than the crown court, leading to estimated savings of up to £40 million a year.
About 85,000 people are in prison in England and Wales, which Lord Thomas has described as a "very, very high" number. He told MPs last autumn that more could be done to explore keeping offenders out of jail, including the use of "very tough non-custodial penalties".
For years magistrates have been calling for increased sentencing powers, but ministers have resisted because of fears that it would swell prison numbers. However, magistrates insist that in a "worst case scenario" the rise in inmates would be no more than 1,000 a year.
Trials in the crown court cost £3,400 a day compared with £900 for those tried in magistrates' courts. Magistrates say that if an estimated 5,514 contested trials and 5,329 guilty pleas that require sentencing were handled by magistrates, there would be a saving in total costs of £30-£40 million.
Malcolm Richardson, national chairman of the Magistrates Association (MA), said that the reform could "be done quickly, without the need for primary legislation." He added that it "would enable more cases to remain in the magistrates court, ensuring that cases are dealt with more quickly and reducing pressure on crown courts. Giving magistrates the power to sentence for up to 12 months would make for swifter, more efficient and more local justice and should be implemented without further delay."