The Welsh giants insist former head of recruitment Iain Moody attempted to gain advanced knowledge of Ole Gunnar Solskjaer's team for the match against Crystal Palace
Cardiff insist Moody, who was formerly Malky Mackay's head of recruitment until his departure in acrimonious circumstances last year, contacted at least three members of club staff before the Premier League relegation six-pointer, which Palace went on to win 3-0.
Moody said he sought to get as much information as possible on Palace's opposition but insisted his work crossed no boundaries.
"That is untrue, completely untrue. Absolutely not - not under any circumstances," he told The Sun.
The Welsh giants believe Moody was hoping to gain advanced knowledge of Ole Gunnar Solskjaer's starting XI prior to the clash, and have made their complaint official.
A Premier League statement read: "The Premier League has received a formal complaint from Cardiff City and will now investigate the matter."