Which? found that the vast majority of advisers in banks and building societies have a poor understanding of investing, and made misleading statements about the features and costs of available products.
Examples included advisers recommending complicated bonds, not mentioning high exit fees and some claiming there was no cost for their advice.
For instance, 17 recommended complicated and high charging investment bonds, with four of the advisers failing to mention that these came with hefty exit fees - sometimes as high as 12% - if you want to get your money out in the first five years.
Of the 37 branch advisers that gave advice in the investigation, 18 claimed that there was no cost for their advice.
Banks and building societies make money through commission paid for the products that they recommend, but only a handful of advisers were upfront about it.
In the worst case, one of the researchers was told by an adviser to invest £50,000 in a bond netting more than £4,400 in commission, this was not disclosed.
Almost half of the advisers failed to mention the Financial Services Compensation Scheme, with others unaware of how much protection consumers receive.
One adviser said the scheme covered £85,000, not £50,000 as is actually the case for investments, while another gave researchers a leaflet detailing the scheme but said they didn't have to read it as the UK banks 'aren't going to go under'.
"Now, more than ever, consumers need advice they can trust on what to do with their money, said Richard Lloyd, executive director of Which?
"It's shocking to see such low standards. It's also disappointing to see that things haven't improved in the past year, despite two high street banks being fined for advice failings and poor complaints handling."
The findings are to be passed on to the Financial Services Authority, with the regulator being urged to punish the worst offenders.
By contrast, it was found that of six independent financial advisers that were put to the test, four gave good advice.
"Our investigation shows that the high street isn't the best place to go for investment advice," Mr Lloyd added.
"If in doubt, consumers should always talk to an independent financial adviser."
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