The officer, who has not been named, appeared before a misconduct hearing this week accused of discreditable conduct.
Details of the case were released on the force’s website. A spokeswoman said the decision not to publish the officers’ name “in this case has been made by legally qualified chair”.
The website said: “It is alleged that whilst using a mobile based dating application the officer asked another user it they wished to participate in sexual activity in exchange for the payment of money and further later identified himself as a police officer. The charge was proved and the officer received a final written warning.”
Police forces have been obliged to hold most misconduct hearings in public since last year as part of an effort to make the service more accountable and transparent.