NBN-related complaints have soared in the past year, with thousands of calls made to the telecommunications ombudsman over delayed connections.

Almost 4,000 calls were made to the ombudsman, with more than 500 of those complaints about missed appointments with technicians.

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Complaints about the broadband network increased every quarter.

Telecommunications Industry Ombudsman Simon Cohen said there had been a breakdown in communication with NBN users.

“A theme in these complaints has been communication breakdown, with consumers often reporting that they don’t know who to turn to solve their problem,” Mr Cohen said.

NBN complaints were also difficult to resolve, with 800 complaints going to mediation.