According to the Ombudsman Services’ third annual Consumer Action Monitor, Glaswegians made 703,455 complaints last year, but 1,353,256 more could have been made.
Across Scotland, retail was the most complained about sector, responsible for more than a quarter (27%) of total complaints, followed by Telecoms (14%) and Energy (12%).
Transport also moved ahead of banking to take the fourth spot, with 10 per cent of complaints.
Instead of complaining, it seems that consumers are voting with their feet.
A fifth (22%) of Scots have taken their custom elsewhere and a similar amount (20%) have reduced spend as a result of bad service, at an estimated cost of £3.2 billion to companies across Scotland last year.
The cost of poorly handled complaints is steep, but a well-handled complaint can improve customer retention.
Three quarters (73%) of Scots say they would be likely to return to a company that handled a complaint well, while just one in 10 (10%) said they would return if their complaint was handled poorly.
Lewis Shand Smith, chief ombudsman at Ombudsman Services said: “Scots are showing good awareness of their consumer rights, but this research shows that a lot more needs to be done to encourage disgruntled customers to make their voices heard.
“Even though businesses are taking steps to improve their customer service, many consumers feel disillusioned and no longer trust them to do the right thing.
“This research has shown that Scots aren’t afraid to vote with their feet, so it is in businesses’ best interests to put customers at the heart of what they do, or face the costly consequences.’’