Just 4% of shoppers claim to have a strong grasp of consumer law, while 47% admit to confusion and a lack of understanding, the poll by price comparison site uSwitch.com found.
The poll found 29% have lost time or money through not understanding their rights, with 41% finding the relevant laws complicated.
It found consumers learn about their rights through the media (52%), trial and error (33%), and from other people (31%), while just 13% learn from their parents and 5% at school.
USwitch said the Government's new Consumer Rights Bill, which aims to clarify and simplify the laws for shoppers and retailers, "may fall flat" if more is not done to educate the public.
The study concluded: "The danger is that, by not tackling consumer education, the Government is likely to fall short of giving consumers the support they really need."
But almost three quarters of consumers (72%) think that plans to extend consumer rights to cover digital content are helpful, while 54% say plans to simplify the network of organisations providing advice and guidance to consumers will make it easier to seek advice and support.
"And with consumers spending many thousands of pounds over a lifetime, this lack of knowledge and understanding is not only a huge disadvantage, but could be financially damaging too.
"The Government's plans to simplify consumer law and to bring it up-to-date are a step in the right direction. However, better protection will only work if consumers actually know about it and understand it too. The Government is in danger of missing the bigger opportunity here, which is to ensure that all consumers are educated about their rights and are made fully aware of what they are entitled to.
"This will not only help them save time and money, but more confident consumers should be able to make better purchasing decisions, which will ultimately help boost competition too."
:: OnePoll surveyed 2,000 UK adults between July 2-4.
Consumer Minister Jo Swinson said: "For too long the rules that apply when buying goods and services have been murky for both consumers and businesses. We want consumers to be confident to shop around and part of this is knowing what their rights are.
"This is why we announced new rights last week. Combined with the introduction of a draft Consumer Rights Bill, this will mean consumers are finally equipped to understand consumer law and that the time spent deciphering this will become a thing of the past.
"Consumers need to know their rights and where to turn to when they have a problem. The Citizens Advice Consumer Helpline is the one place that consumers can now go to for advice on any issue. They can be contacted via www.adviceguide.org.uk or 08454 04 05 06."
Citizens Advice repeated its call for retailers to provide consumer rights information at the till in light of the uSwitch findings.
Citizens Advice chief executive Gillian Guy said: "People are feeling the pinch on their finances so it's important that, if something they buy is not right, they can get it sorted without having to spend another penny.
"All too often shoppers and sales staff aren't quite clear about what people's legal rights are when it comes to getting refunds or exchanges.
"For consumers to get their money back or replacements for faulty goods they need to know and understand what their rights are. That's why, as part of the Government's overhaul of consumer law, we want to see all retailers display consumer rights information at checkouts."