More than 1200 Victorian police officers have been wrongly sworn in over the past eight years due to an administrative bungle, casting doubt over thousands of police matters.

The mistake means some officers have been making arrests without valid powers, with issues arising from the situation being aired in a Melbourne court on Thursday.

Earlier in the day, Chief Commissioner Shane Patton announced he was recently given legal advice about a legislative error in the Victoria Police Act.

He said between July 2014 and August 2021 deputy police commissioners were appointing acting assistant commissioners without the required powers.

Those acting assistant commissioners then swore in a number of graduating police officers.

However, under changes to the Victoria Police Act in 2013, acting assistant commissioners needed to be appointed by the chief police commissioner or a deputy commissioner who had been delegated the authority.

Due to the error, 1076 police, 157 protective service officers and 29 police custody officers have been wrongly sworn in.

Those affected are being contacted, with Victoria Police moving to “urgently swear in” the officers.

Mr Patton said those police would have to be sworn in again before they can perform their duties, with 660 to be re-sworn on Thursday.

“This is an oversight, it’s an administrative oversight, it has some significant consequences for a short period of time,” he told reporters in Melbourne.

The state government is planning to urgently amend the legislation to fix the error, with the laws to be introduced at the next sitting week.

However, parliament does not sit again until March 8, leaving almost two weeks for matters involving unsworn police officers to be contested in court.

The first issues arose within hours of the bungle being revealed, in a case where a police officer is accused of leaking photos of ex-footballer Dani Laidley.

Prosecutor Neill Hutton addressed Melbourne Magistrates’ Court on Thursday, saying issues with whether the investigating officer has been sworn in “may be fatal to the prosecution case”.

“It may not be because the government may fix it up in the interim but we just don’t know,” he said.

Premier Daniel Andrews said the government chose not to put the laws forward when parliament sat on Thursday because it could take time to fix.

“When you’re fixing something that’s particularly glaring you need to take the time to get it fixed right without compounding things,” he told reporters.

Police Minister Lisa Neville said the laws would be retrospective to rectify previous decisions, including arrests or charges issued by unsworn officers.

“We’ve got to get this right, it will rectify all that and all those matters will stand,” she said.

Mr Patton said it was a “case by case analysis” as to whether people could contest arrests or charges by unsworn police officers.

He said some unsworn officers may have been accompanied by police unaffected by the error and “therefore the arrest may be totally valid”.

Ms Neville said there were checks and balances in place in some cases, for example family violence safety notices had to be approved by a sergeant.

Opposition police spokesman Brad Battin said the coalition would support the laws as long as they were “solely designed to fix this error and protect Victoria Police”.

Victoria Police has notified IBAC and the Director of Public Prosecutions.

– AAP