The world's biggest coffee chain is making its first foray into the home of espresso coffee by opening an upmarket roastery in a central Milan square.

Customers walking into the converted post office now housing the lavishly decorated cafe will pay 1.80 euros (1.6 pounds) for an espresso, almost twice the normal market price.

Codacons also said Starbucks' price tag of 4.50 euros for a cappuccino compared with the average Milan price of 1.30 euros.

"These above market prices can cause a damage to Italian consumers who want to have the experience of a coffee at Starbucks," it said in a statement on Thursday.

"We have asked the antitrust (authority) to verify the correctness of Starbucks' commercial practice in its first Milanese store," it added.

Starbucks Global President of Retail John Culver told Reuters the roastery prices reflected "the premium experience" the venue offered.

Starbucks' model offering customers seating space and premium coffee drinks is a novelty for Italians, who are used to drinking their several espresso cups per day while standing at a bar counter.

Starbucks had no immediate comment.

A spokeswoman for Italy's antitrust authority said it would assess the complaint when it had received it.

(Reporting by Valentina Za; Editing by Mark Potter)