Redcar and Cleveland is severing its ties with the Northumbria Tourist Board following claims that it has been made to feel like a poor relation.
The borough council will drop its association with the board and join forces with the Yorkshire Tourist Board from April.
Middlesbrough Council has also revealed it could follow suit.
Last year, Redcar and Cleveland Council voted to include Yorkshire as part of its address and recognise the borough as part of Yorkshire for all cultural, ceremonial and sporting purposes.
It is hoped this latest move will improve the image of the area in the eyes of potential tourists.
The council's tourism promotions officer, Julie Marsden, said: "When people think of Northumbria they think more of Newcastle and Gateshead than East Cleveland, and we have always felt like the poor relations.
"We are very close to the North York Moors and a lot of people tend to cherish the connection with the area."
The chairman of Northumbria Tourist Board, Coun Bob Pendlebury, said he was sorry about the council's decision.
He said: "It is a matter of concern for us. Redcar and Cleveland have been very strong supporters of us for many years and any loss of membership or support in the present climate of change taking place in the structure of tourism and enterprise in the region is of concern."
Meanwhile, Redcar and Cleveland Council is holding a meeting later this month with tourism officials and businesses to discuss ways of improving visitor numbers to the area.
David Andrews, chief executive of the Yorkshire Tourist Board, said: "It is quite natural that Redcar and Cleveland should be marketed under the Yorkshire brand - after all, up until 1974 the area actually was in Yorkshire.
"The local view is that the area has more in common with Yorkshire - its history and heritage is that of Yorkshire."
A spokesperson for Middlesbrough Council said no decision had yet been made on the possibility of it also leaving the Northumbria Tourist Board, but discussions were in progress with the Yorkshire board.
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