Sussex Police Chief Constable Martin Richards is being investigated over an allegation of misconduct.
The Independent Police Complaints Commission (IPCC) are looking into the claims reported to have been made by a member of staff.
Mr Richards has not been suspended.
Sussex Police said that the investigation has been handed over to the IPCC ‘in order to maintain the public’s confidence’ in it’s handling of such allegations.
Chief Constable Martin Richards said: “Given the senior position I hold and the trust placed in me by the people of Sussex and my colleagues, it is absolutely right that the Sussex Police Authority has voluntarily referred this matter to the IPCC for independent scrutiny. I will cooperate fully with the investigation to help them establish the facts.
“With trust in the police at the forefront of ongoing legitimate public interest nationally, I am mindful of the need to conduct my duties with the utmost integrity and an expectation of scrutiny. This is a view shared across the Force and we have recently updated all our policies in this area to underline this commitment.
“While the IPCC investigation is ongoing it will be business as usual. There will be no impact on the service provided to the public or the delivery of operational policing, which is our foremost priority.”
The decision to investigate is a neutral act and does not indicate an assumption of wrong-doing, say Sussex Police.
A spokesperson for the force said: “The Sussex Police Authority and the force strongly support transparency and public scrutiny.
“It is our usual policy to be as transparent as possible where there are allegations of misconduct and we announce involvement in IPCC investigations proactively whenever possible.
“We cannot disclose the nature of the allegations at this time, however, due to the risk of an impact on an ongoing operational matter. We will provide more details when there is no longer a potential impact on operational matters or when the IPCC concludes their investigation.”