Image caption Police and crime commissioner Arfon Jones said the figures "cannot possibly be right"

A police force mistakenly reported 22 homicides in its area over three months when there had only been one.

The error by North Wales Police was spotted by staff working for police and crime commissioner Arfon Jones, who described them as "big city figures".

The force said the "one-off" error occurred in April 2018 after an IT upgrade and was corrected in May.

By then, the figures had already been sent to the Home Office and published by the Office for National Statistics.

Homicide covers murder, manslaughter, corporate manslaughter and infanticide, but not terror attacks.

The incorrect listing of 22 homicides for the fourth quarter of 2017 had confused officers scrutinising the work of North Wales Police.

Mr Jones told a police and crime panel in Conwy the figures "cannot possibly be right - these are big city figures".

"When we saw this, we challenged this and, sure enough, this information is wrong," he said.

Official figures show that in the year to March 2017 there were eight homicides in north Wales, and in the year to March 2016 just three.

Image copyright North Wales PCC Image caption Arfon Jones said people needed to have "confidence in the integrity" of police statistics

The force admitted other mistakes after the change of system - however, these appeared internally and were not published.

They included violence and sexual offences being recorded wrongly.

The new computer system also wrongly recorded 147 homicides from 2013 to 2018 when there had been 33.

A force spokesman said its IT crime systems were upgraded on 7 March, which changed the format of reference numbers.

As a result, some legacy crimes - those from previous years - had been mistakenly counted again as new crimes.

Supt Sharon McCairn apologised, adding: "Our figures for the year to March 2018 inadvertently contained legacy crimes, which had previously been excluded, and this happened while we were upgrading our record management systems.

"As soon as the error was noted in May 2018, the correct data was provided to the Home Office."

She said it was a "one-off mistake" and internal processes had been re-examined to make sure the error would not happen again.

The Home Office will publish the correct homicide figures for the start of 2018 in October.

Mr Jones said: "My staff discovered the problem in the last few weeks as part of my scrutiny of the force.

"It is vitally important that we can have confidence in the integrity of information they produce."