By Sarah Pennells
Handing over cash gives you a contract with the retailer, Which? says.
High street shop staff are fobbing off customers and giving them misleading advice about their rights, according to the consumer organisation Which?
Consumers are often told to take their complaint to the manufacturer, when it is the retailer's responsibility to sort it out, Which? said.
One marketing expert told the BBC that bad advice was often due to a lack of training or the management's attitude.
The government is planning to simplify consumer protection laws.
It says this should mean both consumers and shops are clear about what to expect.
Consumer laws have been strengthened and added to over recent years and shoppers have better protection than ever before.
The problem is that as more laws have been added, confusion has grown.
Now the government is planning a major overhaul of consumer legislation, with the aim of simplifying it.
Consumer affairs minister, Gareth Thomas, said he hoped that both consumers and retailers would be clearer about their rights and responsibilities.
"I think there are real issues about retailers not understanding their responsibilities - perhaps believing that it's the responsibility of manufacturers or that there isn't a problem at all," he said.
"It's because of the complexity of the existing law. If we can simplify the law we can make it easier for high street retailers to understand what their responsibilities are to consumers."
According to Which?, one of the most common problems is retailers telling consumers to take up their complaint with the manufacturer.
But Espe Feuntes, a lawyer with Which?, said the advice was wrong.
"When people purchase goods and they go wrong, for example, and they take them back to the retailer, the retailer is telling them things like - you have to go back to the manufacturer.
"This is actually not right. Your rights are with the retailer. They are the people you have the contract with."
The problem can be systemic and in some cases it is down to a lack of training - or worse - said Professor Robert Shaw, an expert in marketing from Cass Business School said.
"When retailers give out bad information to consumers it can be either due to a lack of training or because of bad attitudes at the top.
"In the case of training, these days it's very often the first budget to be cut.
"In the other circumstance top managers often have a bad attitude to consumers and that then trickles down to the staff."
But it is an accusation strongly denied by the retailer's trade body, the British Retail Consortium (BRC)
"Retailers are not in any systematic way telling their staff to fob customers off or send them to manufacturers when it's actually the job of the retailer to deal with it," said the BRC's Richard Dodd.
Retailers spend millions of pounds making sure that staff understand what customers rights are, he added.
The government's consultation on how to simplify consumer law will continue until the end of July.
More on this story can be seen on Weekend Breakfast on BBC One on Saturday, 5 July from 0600 and on the BBC News Channel at 1035.