Tottenham Hotspur target Stewart Downing handed in a written transfer request to his club Middlesbrough on Monday, although it was rejected by the club.
Boro insist that they will not be selling their top players as they battle against relegation this season and are unwilling to budge on a player who signed a new five-year deal last February.
Chief executive Keith Lamb said: "We received a written transfer request from Stewart this morning. It was considered before being rejected.
"Prior to receiving the transfer request, we received an improved offer for Stewart from Tottenham.
"We immediately rejected this offer and informed Tottenham that Stewart Downing is not for sale and any further interest they have in the player will not be entertained."
The England international is eager to move to White Hart Lane and following Boro's rejection of a "derisory" £6million offer from Spurs, Downing has taken steps to force through his departure from the Riverside Stadium.
Tottenham have been on Downing's trail for several years and had already had a series of bids turned down, and it remains to be seen whether or not they test Boro's resolve to hang on to the player - or indeed, their patience - by returning once again.
It is understood Spurs' latest offer amounts to in excess of £11million, although the Teessiders value him at closer to £15million.
Tottenham manager Harry Redknapp confirmed that his club are trying to hammer out a deal for to acquire Downing but insisted that the final say on any transfer would be Boro's.
"The club made an offer and I know the chairman has made a big offer for him," Redknapp said. "We can only make an offer and it is up to the clubs if they want to accept it or not.
"Middlesbrough are a good club and if the chairman (Gibson) decides he doesn't want to sell him, that's his right to do that and that's the end of that one."
Downing's father revealed that his Boro-born son had thought long and hard about handing in his transfer request but felt that his childhood club could no longer match his ambitions.
"Stewart's been frustrated since the summer, really," Downing Sr, told the Evening Gazette. "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.''
Downing signed a five-year contract last February but when Ayegbeni Yakubu handed in a transfer request to force through a move to Everton, Boro boss Gareth Southgate decided there was no point in hanging on to a player who did not want to be there.
However, it is expected that Gibson will reject Downing's transfer request and on Sunday night the Boro chief broke his silence regarding Spur's pursuit of his player.
"I can confirm we have received an offer from Spurs for Stewart Downing and I can also confirm we have rejected that offer," Gibson said. "I've spoken to Daniel Levy and told him categorically that their interest is not welcome.
"I've also told him we will not entertain any further offers for Stewart or, for that matter, any other senior member of our squad. The same applies to Tuncay and it also applies to Gary O'Neil.
"I repeat: none of our senior players will be leaving the Riverside Stadium this month. We've got a talented group of players and it's time for us to knuckle down and focus on the job in hand. As far as we're concerned, this is now an end to the matter."
On Sunday, Southgate claimed Downing, 24, remained unaffected by speculation over his future following his starring role in the FA Cup victory over Barrow.
The Boro boss said: "Stewart played in the middle of the park for us on Monday night (at Manchester United) and I think it has given him something else to focus on. It has given him a freshness and I think it gave us a bit more creativity."
Southgate is under no pressure to sell, although he had made no secret of the fact that he will have to raise his own funds if he wants to buy this month.
Teesside-born Downing has won 21 senior England caps to date, the last of them in the 2-1 win over Germany in Berlin in November, and has made 164 appearances for Boro since making his senior debut in 2001.