The full-back completed his return to the Stadium of Light on Monday, with the Hammers stating they were unable to stand in his way after he handed in a written transfer request.

The Northern Ireland international has since rejected that version of events and accused the West Ham board of "trying to cover their tracks".

Now the club have responded, again insisting their hand was forced by McCartney's desire to move on.

A statement on the club's official website said: "Having previously declared their interest, Sunderland approached West Ham United at the end of last week with a renewed offer to sign the player.

"Both McCartney and his agent were made aware of this development.

"However, as was demonstrated by the rejection of a previous bid and with the subsequent agreement of a new five-year contract, West Ham United had no intention of selling McCartney.

"Following this offer from Sunderland, McCartney handed in a signed written transfer request on Monday September 1, which stated 'due to private, family reasons I wish to accept the offer to move back to Sunderland AFC'.

"West Ham United are astonished by the claims made subsequently by the player that there was no written request to leave with McCartney having also repeatedly spoken of his desire to return to Sunderland to both the manager and senior club officials.

"On Sunday August 31, a senior club official wrote to McCartney stating 'no-one wants to sell. If you are happy to stay, great, it ends here. I thought you were unhappy and wanted to go'.

"The player then restated his desire to leave before handing in the written transfer request on Monday."