An official report into Britain's cities should be re-issued - with a correction acknowledging that Wolverhampton is not part of Birmingham, according to an MP.
The study, which will be used by the Government to carry out a revolution in local government, counted Wolverhampton, Walsall, Dudley and Sandwell as part of Birmingham.
It was commissioned by Local Government Minister David Miliband, who is preparing to publish plans for a city region based around Birmingham.
This could have the power to raise its own budget through a regional tax, and one of the options being considered is to create a directly-elected mayor to run it.
The report, called The State of the English Cities, was written by Prof Michael Parkinson, from Liverpool John Moores University.
It identified 56 "primary urban areas" which could form the basis of city regions.
The Black Country, Solihull and Birmingham were all included in a "Birmingham" region, although Wolverhampton is a city in its own right.
Warley MP John Spellar (Lab), a former Minister, asked for an errata slip to be added to the report.
In a House of Commons question, he asked John Prescott, the Deputy Prime Minister, "if he will publish an errata slip for the publication English Cities to acknowledge the existence of the boroughs of Walsall, Wolverhampton, Dudley and Sandwell".
The question was answered by Local Government Minister Phil Woolas, who said the boundaries used in the report reflected the physical boundaries of built up areas.
He did not directly address the request for a correction.
The demand illustrates the strong feelings the issue of a city region can arouse.
Mr Miliband has pledged that no town or city will lose its own distinct identity, and new local government arrangements will be agreed with local residents rather than forced on them.
He said the aim was to improve the way decisions about transport and economic development, which already cross local authority boundaries, are taken.
But any possibility that neighbouring towns or cities might be incorporated into a "Greater Birmingham" could arouse strong opposition.