For the review which came into effect for the 2010 general election, the four authorities were considered separately, with Middlesbrough and Redcar and Cleveland being combined.
[1][2] For the 2023 Periodic Review of Westminster constituencies, coming into effect for the 2024 United Kingdom general election, the Boundary Commission for England considered the area comprising the Tees Valley Combined Authority, which also comprises the unitary authority of Darlington, as a sub-region of the North East Region.
At the time of its creation, Cleveland contained the equivalent of approximately 6 constituencies: four boroughs contained within the County Borough of Teesside, namely Stockton, Thornaby, Middlesbrough and Redcar; Hartlepool in the county of Durham; and the majority of Cleveland and Whitby in the North Riding of Yorkshire.
[1][2] For the 2023 Periodic Review of Westminster constituencies, which redrew the constituency map ahead of the 2024 United Kingdom general election, the Boundary Commission for England opted to treat the area comprising the Tees Valley Combined Authority, which includes the unitary authority of Darlington, as a sub-region of the North East Region.
Stockton West included some rural areas of the Borough of Darlington (previously part of the abolished constituency of Sedgefield).