Darren Oakey pleaded guilty to one count of fraud by false representation, perverting the course of public justice and obtain/disclose personal data/information.
The 51-year-old, of Sayers Road in Stafford, who was previously an inspector based at the force’s headquarters, was convicted at Stafford Crown Court on Friday.
An investigation by Staffordshire Police’s Anti-Corruption Unit found that on July 1, 2016, he dishonestly claimed mileage to and from a London Pride pre-event and the London Pride march, where he was to represent Staffordshire Police.
The following May perverted the course of pubic justice by submitted four photographs to officers investigating his conduct. Oakey claimed to have taken personally the photos at London Pride when he hadn't.
Between May 2013 and August 2015, Oakey, without the consent of the data controller, knowingly or recklessly obtained or disclosed personal data or information.
He was suspended in January 2018 before resigning in June.
Chief Constable Emma Barnett said: "Darren Oakey was working in a position of trust. He betrayed that trust and let down his colleagues and the police service.
"His suspension and prosecution reinforce the fact that Staffordshire Police is committed to the highest levels of ethical policing and integrity.
"We take offences such as this incredibly seriously and once his offending came to light he was quickly suspended from duty and his access to any information systems removed.
"Any staff member of Staffordshire Police suspected of a criminal offence will be thoroughly investigated."
Oakey will be sentenced at Stafford Crown Court on November 19.