Stewart Downing's father has claimed his son has little choice but to leave Middlesbrough if he wants to fulfil his ambitions. The 24-year-old this morning handed in a transfer request with Tottenham stepping up their long-held interest in the England international. The Boro chairman Steve Gibson has insisted in recent weeks that the academy graduate ? or anyone else for that matter ? is not for sale, but Downing, who signed a new five-year deal in February last year, is desperate to quit the Riverside Stadium. His father, Stewart Sr, told the Evening Gazette newspaper: "Stewart's been frustrated since the summer, really. "When he signed his new contract he was assured that there would be significant investment in the squad. "He feels that the club haven't matched those expectations. He's also frustrated that the team is once again struggling in the Premier League. "Obviously as a Middlesbrough lad he's thought long and hard about the decision to hand in a transfer request, and he also hopes the fans will understand his reasons for doing so." Spurs are now understood to have offered in excess of £11 million (Dh58.4m) for the winger, a player they have been trailing for several years, with the north London club short of attacking options down the left-hand side.