The Local Government (County Boroughs and Adjustments) Act 1926 (16 & 17 Geo.

The consequent loss of population and rate base affected the finance of county councils.

On 16 February 1923, a royal commission had been appointed under the chairmanship of the Earl of Onslow to "inquire into the existing law and procedure relating to the extensions of county Boroughs and the creation of new County Boroughs in England and Wales, and the effect such extensions or creations on the administration of the Councils of Counties and of non-County Boroughs, Urban Districts and Rural Districts; to investigate the relations between these several local authorities; and generally to make recommendations as to their constitution, areas and functions".

[1] The commission published its first report in 1925, and among their recommendations were that: The 1926 Act implemented most of the commission's recommendations by making the following changes: The last county borough constituted under the 1888 Act was Doncaster, with a population of about 60,000, in 1927.

The population limit for county boroughs was raised to 100,000 by the Local Government Act 1958.