Newspaper reports have suggested that Yakubu requested a transfer from the Riverside after Everton tabled a £10million offer for the Nigerian international.
Yakubu has become unsettled on Teesside in recent months and a number of clubs have reportedly made enquiries over the summer, including Manchester City, Portsmouth, West Ham and Aston Villa, with Boro already rejecting bids for the striker.
Middlesbrough chief executive Keith Lamb has now moved to quash the speculation by stating that Yakubu will not be leaving after manager Gareth Southgate reassured him of his future.
"Naturally all of the speculation over such a long period has unsettled Yakubu a little," Lamb told the club's website.
"But Gareth Southgate has made it absolutely clear to Yak that he has a major part to play in the club's future and we have no plans to sell him.
"The truth is that there has been no bid from Everton in any case, so we want Yakubu focused on Saturday's game with Blackburn and the season ahead."