Last year, McGregor’s McGregor Sports and Entertainment Ltd filed the application ahead of McGregor boasting after his Floyd Mayweather boxing fight that his ‘Notorious’ brand whiskey was “coming soon”.

However, McGregor’s firm has now withdrawn the trademark application at the European Union Intellectual Property Office (Euipo) in Spain in the face of opposition from a Carlow brewer.

Last year, founder of the Carlow Brewing Company, Seamus O’Hara formally objected to Mr McGregor’s firm registering the ‘Notorious’ trademark.

Mr O’Hara had already registered the ‘Notorious’ brand for selling alcohol in 2016 and his representatives told the EUIPO that the identical nature of the ‘Notorious’ trademark “is expressing prohibited by trademark law”.

Mr O’Hara’s representatives said that his own Notorious trademark and the one proposed by Conor McGregor’s firm “cannot coexist peacefully in the market”.

It is understood that Carlow Brewery has had no approach to date from Mr McGregor’s side on purchasing the ‘Notorious’ trademark.

Now, Mr McGregor’s firm has formally notified EUIPO that it has withdrawn its ‘Notorious’ application.

EUIPO has written to Mr O’Hara’s representatives informing them of the move and has told the McGregor firm to pay €620 in costs to Mr O’Hara.

Mr McGregor - with an estimated net worth of €85m - may now have to change the name of his planned whiskey unless he makes Mr O’Hara an offer he can’t refuse to buy the 'Notorious' brand for alcoholic drinks or make a fresh trademark application with EUIPO where success is in no way guaranteed.

However, the move to withdraw the ‘Notorious’ application is not expected to impact on Mr Mr Gregor’s plans to launch a whiskey here.

In a recent Instagram post - just days after the ‘Notorious’ trademark application was withdrawn - the MNA fighter posted: “Working hard at my Whiskey distillery. It is in my opinion, the finest distillery we have on this great island."

He said: “We have the purest soil, with the freshest Irish spring water, and our golden Irish grain and malt is so golden… I respect Jameson, the current number one. But I am coming in strong. I am coming in passionate. I am coming to take over!"

He added: “Seventy-seven acres of un-matched Irish soil. Creating an un-matched Irish whiskey. We are producing nothing but liquid gold here. Proper liquid gold.”

McGregor last year brandished a bottle of whiskey with the brand ‘Notorious’ on the label. However, in his Instagram post, the word ‘Notorious’ was conspicuous by its absence.

Mr O’Hara did respond to a request for comment yesterday.