Average sentence lengths for violent and sexual offences in England and Wales fell steeply last year as the Covid pandemic also led to a huge slowdown in the number of people dealt with by the criminal justice system.

The average custodial sentence length for violent crimes fell by 22% to 18.5 months and the figure for sexual offences fell by 12% to 52 months, the lowest figure since 2011, according to official figures.

Sentence lengths fell in all categories, except for public order offences and “miscellaneous crimes against society”, which both increased slightly.

The surprise falls, which come despite government rhetoric about being tough on crime, were revealed in a Ministry of Justice report that lays bare the chaos caused by the coronavirus pandemic in the criminal courts.

The number of criminal defendants brought before the courts in England and Wales fell by nearly a third in the year to March 2021 from a record low in 2019. The number of indictable offences heard was down 14.2% and the number of summary offences down 36.5%. The number of defendants convicted was down 33.8%.

Of all potential outcomes, the only rise was in the use of community resolutions, which were up 16.5%. Community resolutions have proven controversial, and there are fears that they are being used increasingly for serious crimes to avoid putting more strain to the courts.

“While out-of-court disposals can be effective in reducing reoffending for minor offences, they must not be seen simply as an alternative to court, especially for sex offences or other serious crimes,” said the chair of the Bar Council, Derek Sweeting QC.

Overallthe criminal justice system dealt formally with 1.07 million people in the year to March, including out-of-court resolutions, a 28% fall from 1.59 million the previous year.

The number of people charged by police remained broadly flat, down 1%, leading lawyers to warn of a backlog of cases that will take years to clear. The number of outstanding crown court cases in the first quarter of 2021 was up 45% on the same period last year, according to MoJ figures published June.

At the same time the number of defendants remanded in custody was at a five-year high, according to Thursday’s figures, implying that thousands of innocent people may have languished in jail because of delays.

The reason for the fall in the length of custodial sentences was not immediately clear, and the government insisted plans to toughen sentencing for convicted sex offenders remained on track.

“We are changing the law so that sexual offenders face more time behind bars, and our rape action plan will increase the number of cases reaching court while bolstering support for victims at every stage,” a spokesperson said.

The chair of the Criminal Bar Association, James Mulholland QC, suggested shorter sentences could be the result of new guidelines circulated during the pandemic.

“While sentencing principles a year ago required judges to be mindful of the potential for prison overcrowding, the reality is that a failure to invest to have sufficient court rooms open for trials has resulted in record low numbers of people being tried at all,” he said.

“That has left the sentenced prison population at a decade low, while those on remand, mostly awaiting trial, now account for nearly one in five of all prisoners.”

About 15% of those on remand would subsequently be cleared, he said.