The police and crime commissioner of one of England’s most troubled forces is being investigated over an allegation of a historic sexual assault.

Steve Turner, who became Cleveland police and crime commissioner in May, is resisting pressure to resign after the revelation by the Mirror newspaper.

Turner, a Conservative, was already in the spotlight after he was named in parliament as having been cautioned some years ago for theft when he worked at a supermarket.

His job gives him oversight of Cleveland police, which in 2018 became the first English police force to be rated inadequate across all areas.

The police watchdog, the Independent Office for Police Conduct (IOPC), has now begun an investigation into the allegation of a historic sexual offence, which will be carried out by another force.

An IOPC spokesperson said: “Any allegation that a criminal offence may have been committed by a police and crime commissioner (PCC) must be referred by the appropriate authority to the IOPC to determine whether the matter should be investigated.

“We have now begun a managed investigation after a complaint referral from the Cleveland Police and Crime Panel regarding the alleged conduct of the current PCC prior to taking up the role.

“This investigation, which follows an allegation of a serious non-recent criminal offence, will be carried out by a force from another area under our direction and control.

“We have contacted the complainant to make them aware of our involvement. As this investigation is at a very early stage, it would not be appropriate to comment further.”

The IOPC is also assessing whether or not action is required in relation to the theft, a spokesperson said.

Turner’s office said he has no plans to resign or temporarily step down.

His predecessor, Barry Copinger resigned in September 2020 after the county’s chief constable Richard Lewis raised concerns about a freedom of information (FoI) breach.

An investigation by the Information Commissioner’s Office (ICO) concluded Coppinger did not commit a crime by deleting WhatsApp messages on his phone.

In August the IOPC said former Cleveland police chief, Mike Veale, would face gross misconduct proceedings.

There was “sufficient evidence” he breached professional standards while leading the force, the IOPC said.

Veale, who quit Cleveland police in 2019 after just a year in post, led the Sir Edward Heath inquiry while at Wiltshire police.

The office did not disclose the nature of the alleged misconduct but it has previously said it was looking into complaints of “inappropriate behaviour towards colleagues, discrimination, and unprofessional behaviour”.

Cleveland police is currently seeking yet another police chief constable – its seventh in nine years – after Lewis announced he was leaving to rejoin Mid-Wales police at the end of the year.