The phrase "alleged monopoly" is correct and usable in written English.
It can be used when discussing a situation where a company or entity is accused of having a monopoly, but it has not been proven or established as fact.
Example: "The government is investigating the alleged monopoly held by the tech giant in the software market."
Alternatives: "supposed monopoly" or "claimed monopoly".
A very public spat between Mr Slim (who wants to enter the television market) and a pair of broadcasting billionaires (who want more of the phone business) has seen each complain of the unfairness of the others' alleged monopoly.
HEARING TO REOPEN NOV. 10 Board Investigating Alleged Monopoly Hears of International Western's Foreign Holdings.
As a commissioner, Ms. Jones was also involved in an effort by the F.T.C. to break up an alleged monopoly of cereal makers and an effort to persuade the garment industry to put care instructions on clothing labels.
But purchasing its lesser cousin was really about something bigger fighting off the latest legal threat to the NCAA's alleged monopoly on college sports.
Last month, China's State Administration for Industry and Commerce - the body responsible for enforcing business laws - said it was looking into "alleged monopoly actions" by US tech firm Microsoft.
Very few claimed a monopoly of wisdom for their candidate, or alleged a monopoly of wickedness on the other side.
To protect the farmer from alleged wheat trade monopolies by speculators and officials, the league demanded state-owned mills, grain elevators, banks, and hail insurance companies.
Same with, say, Monopoly.
A year earlier, in 2005, an Antwerp-based courier business, Monstrey Worldwide Services, which once had a near monopoly on diamond deliveries, was alleged to have misused customs-free zones in places like Geneva to smuggle stones.
It may be that, even without an alleged sexual predator in the race, a conservative monopoly on the highest political offices doesn't have to be a foregone conclusion.
During City Council hearings on a series of permit-related appeals, rival companies have alleged the city's current operators have a monopoly on taxi operations.
