Police investigating Andrew Mountbatten-Windsor want witnesses to contact them if they believe they have information about alleged sexual misconduct, corruption, fraud or the sharing of confidential information involving the king’s brother.

In a sign of the potential expansion of their “unprecedented investigation”, Thames Valley police vowed to rigorously investigate claims against the former Prince Andrew.

Mountbatten-Windsor, 66, was arrested and questioned under criminal caution in February on suspicion of misconduct in public office, related to his role as a British trade envoy.

He is alleged to have passed information to the disgraced financier Jeffrey Epstein, according to claims arising from the documents released by the US Department of Justice. The former prince denies all wrongdoing.

Assistant chief constable Oliver Wright said Thames Valley police (TVP) were already working through a “significant amount” of information from a range of witnesses.

But the force is concerned that people who may have information about criminal offences wrongly think detectives are interested in only one narrow aspect, namely the alleged passing of confidential information.

Stoking their concerns about other potential allegations are a series of claims about the former prince’s conduct already made publicly, such as in the media. Police have not yet been contacted by witnesses they believe may be out there.

Police stress that misconduct in public office (MIPO) covers a range of offences, including sexual misconduct, wilful neglect of duty, perverting the course of justice, and dishonest or fraudulent conduct, among many others.

Wright said: “Misconduct in public office is a crime that can take different forms, making this a complex investigation.

“Our team of very experienced detectives are working meticulously through a significant amount of information that has come in from the public and other sources. We are committed to conducting a thorough investigation into all reasonable lines of inquiry, wherever they may lead.

“We encourage anyone with information to get in touch with us through the normal non-urgent contact channels, such as the Thames Valley police online portal.”

It is understood information has already or will be obtained from the royal household and government departments, such as those involved in the former prince’s appointment as a trade envoy. Detectives are expected to seek documents and witnesses about what was expected from the trade envoy role in terms of behaviour and ethics.

TVP are also expected to seek information from the Metropolitan police, which assessed claims against the king’s brother twice and declined to investigate. The Met provided his armed bodyguards while he was officially a working royal, a status he lost amid the outrage over his friendship with Epstein.

The TVP investigation includes detectives with expertise in sexual offences. The force is still assessing a claim from a woman that she was taken to an address in Windsor in 2010 for sexual purposes. It is not a full criminal investigation yet. The woman lives in the US and detectives have contacted her through her lawyer.

Wright said: “We have engaged with the woman’s legal representative to confirm that, should she wish to report this to police, it will be taken seriously and handled with care, sensitivity and respect for her privacy and her right for anonymity.

“We recognise how difficult it can be to speak about experiences of this nature, and any contact with police will be led by her wishes, when and if she feels ready and able to do so.”

Wright said police would listen and investigate “when she feels ready and able … to come forward and talk to us”.

The investigation is expected to be long, with no criminal trial until 2027 if it were to produce evidence to support criminal charges.

Three British forces are conducting full criminal investigations triggered by other revelations in the Epstein files, with several others assessing claims about flights linked to the disgraced financier entering the UK.

Police investigating the former Prince Andrew believe obtaining the original Epstein documents is “hugely important”. Currently they and other UK forces have only printouts from the DoJ website. US authorities have declined to hand the original documents over and told British police to submit a formal international legal request for assistance, which could take months, if it is agreed to at all.

As well as the TVP investigation into Mounbatten-Windsor, the Met is investigating Peter Mandelson for misconduct in public office, and Surrey police this week announced they were investigating claims of historic child sexual abuse arising from the Epstein files.

After Mountbatten-Windsor’s arrests, police conducted a short search of his Norfolk home and a week-long search on the Windsor estate where he lived for decades. Materials seized are still being examined.

One key aspect for police is obtaining evidence proving that the former prince’s role as a trade envoy is covered by MIPO rules.

Police have held early discussions with lawyers from the Crown Prosecution Service, which authorises criminal charges in England and Wales.

TVP have not officially named Mountbatten-Windsor as the man they arrested in February.