The findings have been made by three psychology lecturers from Worcester College of Higher Education who hired male actors to reproduce police interviews with suspected armed robbers and cheque fraudsters.
The actors used the Birmingham - or "Brummie" - accent and standard accents for the test and the suspect's guilt was judged by 119 students.
The results showed a bigger bias against Brummie accents than was the case with differences in race.
"The Brummie suspect was regarded as less intelligent, more likely to be poor and working-class and less socially competent," said Berenice Mahoney.
Someone with a Brummie accent was more than twice as likely to be convicted of the crime than a suspect with a standard accent.
"Past research has tended to find that people who use regional accents are frequently seen as more friendly, warm and kind. But we didn't even find our Brummie was regarded in that way. The Brummie accent does come out particularly badly," said Dr Mahoney.
"Accents like Geordie and Mancunian seem to come out quite well but the Brummie has tended to stay along the bottom ... It's all to do with power and what's regarded as socially acceptable. What we found quite startling was that people are willing to
Dr Mahoney warned: "This was a preliminary study and the results should be treated with caution. But it would be naive of us to think this is not happening with magistrates, police officers and jurors involved in the legal process. The extent to which it is happening is one of the things we need to establish.
"It's just another example of a prejudice we need to tackle. I don't think there is an easy solution but at least if people are aware it exists there is a chance of re-educating those involved in these decisions."
This is the first research in Britain linking regional accents with possible bias in the legal system.
John Dixon, one of Dr Mahoney's co-researchers, carried out a similar study in South Africa three years ago which found that someone using a regional dialect was more likely to be convicted of a blue-collar crime. But the results of the Worcester survey showed the Brummie accent was equally likely to be blamed for the white-collar cheque fraud as the blue- collar armed robbery.
The survey's findings will be presented at a British Psychological Society conference in Cambridge next week.Reuse content