TOKYO (AFP) - A consumer group is warning Japanese men to exercise extreme caution before undergoing foreskin surgery after a spate of eye-watering mishaps on the operating table.

In a report definitely not for the squeamish, the National Consumer Affairs Centre (NCAC) revealed customer service and other bodies received over a thousand complaints across Japan between fiscal 2011 and 2015.

They were spurred by complications caused by men opting to treat phimosis - a narrowing of the foreskin's opening that prevents it from being fully retracted - with a quick snip.

A large proportion of the 1,092 complaints came from patients in their teens to 30s, said the NCAC, which is consequently advising men to think carefully before going under the knife.

The painful issues caused by surgical blunders included swelling, heavy bleeding, tissue decay and erectile dysfunction, the NCAC explained in a report that will make many readers wince.

Among those left hopping mad were men who answered advertisements offering phimosis surgery for between around US$500 and US$1,000, only to be told by clinics that "cheap surgery could cause a shabby appearance" to the penis, according to the report.

Subsequently, many of those establishments recommended procedures costing over US$10,000 with numerous patients signing paperwork and undergoing surgery the same day.

"Ask for a full explanation of the risks involved," the NCAC website advises.

"Avoid unnecessary medical procedures and think seriously before agreeing to surgery on the same day as diagnosis unless in an emergency."

The report also mentions that further side effects from heavy-handed surgery included anxiety, and concludes that the pitfalls of opting to use cut-price clinics far outweigh any potential saving.