Sunderland have defended themselves against claims that they have made an illegal approach to West Ham striker Demba Ba.
The Hammers have reported the Black Cats to the Barclays Premier League over an allegation that they have breached the rules governing transfers.
However, a spokesman said: "Sunderland AFC is fully aware of the Premier League regulations pertaining to player recruitment. If we are interested in any player currently under contract with another club, we will speak directly to that club, in line with the regulations."
A Premier League spokesman confirmed that they have received a complaint from the Hammers' which will now be considered.
He said: "We have received a letter from West Ham United. We will look into their complaint to see if there is a case to answer."
The regulations are detailed in Section K of the Premier League rulebook and state that a club cannot approach a contracted player at another club either directly or indirectly without prior written consent.
Indeed, even a public statement expressing an interest in a player can be construed as an offence.
Sunderland are one of a series of clubs - derby rivals Newcastle are among the others - to have been linked with Ba, who scored seven goals in the Hammers' ultimately vain bid to retain their top-flight status following a January move from German club Hoffenheim.