From Longman Dictionary of Contemporary Englishdeclare an interest (in something)declare an interest (in something)CONNECTED WITHINTERESTEDto officially state that you are connected with something or someone, and so cannot be completely fair and independent when making a decision involving them → interest
Examples from the Corpus
declare an interest (in something)• Leeds manager Howard Wilkinson has already declared an interest in him after he spent a week training at Elland Road.• Mr. Adley: I have already declared an interest.• Mr. Adley: I thank my right Hon. Friend for that reply and declare an interest in the industry.• If you have strong feelings about a situation declare an interest and suggest that some one else temporarily takes the chair.• It's probably best to declare an interest. 