The Everton manager is adamant that, even should "a Gareth Bale-size valuation" be tabled for the young midfielder, the Toffees will not disrupt their top-four push.
The midfielder, who turned 20 in December, has emerged as one of the Premier League's hottest properties this season and broken into the England squad, underlining his starlet status with a decisive free kick against Swansea City on Sunday.
Barkley's form has fueled speculation of a potential move to one of Europe's elite clubs, but Martinez is adamant that no disruption to his side's top-four push will be accepted.
"Ross is in a moment of his career where, first, he knows that he needs to carry on developing and this is the perfect place to do that," the Spaniard told the media. "Second, he is a mad Evertonian and enjoying every single second, and third, we are in the middle of a season where we would never, ever consider disrupting what we have got in our squad now.
"It is not the right time for the player or the club to consider anything. Even if we got a Gareth Bale-size valuation we would never even consider it in January."
Martinez said that even if suitors come on strong, the club is still in control.
"What is very important is that if anything happens, it is our club that dictates how and when," he added. "If we had a financial problem or were facing a financial disaster then we would not be in control of those aspects and I would be telling you: 'Look, we are in the lap of the gods.'
"We are not in that situation at all. We are probably in the strongest financial position we have been for a long time.
All we are going to make is football decisions. If we were going to lose a player it would be to end up with three or four replacements and in a stronger position. That is always the case."
The manager also talked about the midfielder's importance to the club.
"Ross is an icon for us. He represents everything we are trying to do this season so, even if a stupid offer arrived in January, it would never affect us. It is important for us as a football club to show we are making the right football decisions," he said. "There is no question mark over Ross's future; he is in the best moment of his time and is everything we want a player to represent at Everton. There is not even a question mark against whether he is going to be here in February or not."