“Why is there only one Monopolies Commission?” is a joke that appears to have started in the United Kingdom in 1978 (the Google Books date might be incorrect) or in 1981. Conservative political commentator Mark Steyn wrote in 2011, “In fact, it’s an incisive observation on the nature of government. We wouldn’t like it if there were only one automobile company or only one breakfast cereal, but by definition there can be only one government.”
 
The UK’s Competition Commission replaced the Monopolies and Mergers Commission in 1999.
 
       
Wikipedia: Competition Commission (United Kingdom)
The Competition Commission is a non-departmental public body responsible for investigating mergers, markets and other enquiries related to regulated industries under competition law in the United Kingdom. It is a competition regulator under the Department for Business, Innovation and Skills (BIS). It ensures healthy competition between companies in the UK for the ultimate benefit of consumers and the economy.
 
The Competition Commission replaced the Monopolies and Mergers Commission on 1 April 1999. It was created by the Competition Act 1998, although the majority of its powers are governed by the Enterprise Act 2002.
 
Google Books
Punch
Volume 275
1978
Pg. 429:
“Is there only one Monopolies Commission?”
 
Google News Archive
21 December 1981, Glasgow (Scotland) Herald, “Monopolies’ probes deep behind the merger scene” by Kenneth Campbell, pg. 9, col. 4:
And sooner or later, someone has to ask the question: Why is there only one Monopolies Commission?
 
New Scientist
“Joke” joke
22 August 1998 by Douglas Porter, Kenninghall, Norfolk
Magazine issue 2148
A reader quoted the joke “Why is there only one Monopolies Commission?” and asked whether the joke “Why is there only one Monopolies Commission joke?” was paradoxical, insofar as it created a second Monopolies Commission joke and thereby invalidated itself.
 
The answer is, of course, that it doesn’t. The second joke is not a joke about the Monopolies Commission but about Monopolies Commission jokes, and therefore is not itself a Monopolies Commission joke. There is scope for a further Monopolies Commission joke which would invalidate the Monopolies Commission joke joke, but naturally not the Monopolies Commission joke.
 
OCLC WorldCat record
Why is there only one Monopolies Commission? : British art and its critics in the late 1970s
Author: Neil Mulholland
Dissertation: Thesis (Ph.D.)—University of Glasgow, 1998.
Edition/Format: Thesis/dissertation : Thesis/dissertation : Manuscript Archival Material : English
 
OCLC WorldCat record
Why is there only one Monopolies Commission, but over forty Information Management Associations in the United Kingdom?
Author: Colin Theakston Affiliation: Faculty-Librarian, Durham Business School, School of Economics, Finance and Business, Durham University, Mill Hill Lane, Durham, DH1 3LB, UK
Edition/Format: Article : English
Publication: International Journal of Information Management, v26 n5 (2006): 357-359
Database: ScienceDirect
Other Databases: ArticleFirst
 
Google Books
After America:
Get Ready for Armageddon
By Mark Steyn
Washington, DC: Regnery Publishing, Inc.
2011
Pg. 47:
There was an old joke in Britain: “Why is there only one Monopolies Commission?” In fact, it’s an incisive observation on the nature of government. We wouldn’t like it if there were only one automobile company or only one breakfast cereal, but by definition there can be only one government—which is why, “when the government’s monopolizing,” it should do so only in very limited areas.