Barkley's sparkling form this term has seen him break into the Toffees' first team and earn himself a spot in Roy Hodgson's England squad for the World Cup in Brazil.
The situation is similar to that of Wayne Rooney, who travelled to Euro 2004 with England as an Everton youngster and moved to Manchester United later that summer, but Martinez is adamant Barkley is going nowhere and believes staying at Goodison Park will aid his development.
"It would be wrong for him (to leave this summer)," the Spaniard told several national newspapers.
"I always feel as manager you develop a relationship with players and you're always honest with that.
"Ross is a phenomenal talent - probably the best English talent I have ever seen - but he is not the finished article yet.
"In football obviously you can never speak about the future. Obviously we need to come along and try to get into the top-four positions to offer players like Ross the next stage of their development.
"Ross is delighted at Everton and feels very much that he is in the right place at the right time of his career."
A starring role for England this summer would increase talk of a potential move while raising Barkley's profile even higher, but Martinez does not expect to see a change in his attitude.
"He's playing at a World Cup and he could be in a position to impress millions, never mind just the people in England," he said.
"That's the type of tournament we are talking of. But Ross will never look at it in that way. He will look at it and try to be as good as he can to help England.
"Ross will come back the same person - I can guarantee you that.
"He's not someone who will lose sight of realism when he comes back. For us he's a star whatever happens in the World Cup. He is ready now to fulfil whatever role the England manager wants to give him."
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