Mendieta has "apologised unreservedly for any upset which may have been caused".
Gaizka Mendieta: “I want to apologise for what has been written, supposedly in my name.
“I never said that and I am upset that the Spanish journalist has twisted it to sound like I did. It’s very annoying.
“It’s not what I said at all. What I told the reporter was that I heard from team-mates and others that this was the sort of thing that had happened in the past.
“But I certainly never saw it when I was at Middlesbrough.
“Things like that didn’t happen when I was at Middlesbrough.
“I never saw any sign of a drinking culture there.
“Everything was always very professional under both Steve McClaren and Gareth Southgate.”