Miall, who was at Metro International for more than four years, was reuluctant to divulge details about his new role except to say that it would be for a French publisher, that it had venture capital backing, and that it was not connected with the London freesheet market.
He said: "I wouldn't be leaving my job unless it was for something really worthwhile. The product is amazing and it's going to be very successful."
Alistair Ballantyne, head of UK sales, has been promoted to Miall's position with immediate effect.
Miall's departure follows the exit last month of Michael Craig, Metro International's global key account director, who joined News International to head advertising for its planned free newspaper.
Metro International does not publish in the UK, but is understood to be interested in the London afternoon newspaper contract.
He said: "I wouldn't be leaving my job unless it was for something really worthwhile. The product is amazing and it's going to be very successful."
Alistair Ballantyne, head of UK sales, has been promoted to Miall's position with immediate effect.
Miall's departure follows the exit last month of Michael Craig, Metro International's global key account director, who joined News International to head advertising for its planned free newspaper.
Metro International does not publish in the UK, but is understood to be interested in the London afternoon newspaper contract.