Sluggish internet speeds are driving more complaints from Australians than those about patchy mobile services.

Internet-related complaints to the industry ombudsman have hit a five-year high, surging by more than a fifth between July 2015 and June 2016. More than 112,000 new complaints were lodged with the Telecommunications Industry Ombudsman during the year about landline, mobile and internet services. Complaints about mobile services fell by…