“People equate the Birmingham accent with being untrustworthy,” he said. “But the link with intelligence is simply a stereotype. There is no link between regional accent and intelligence.”

He added: “Whenever I have been to Birmingham I found the people to be very bright and friendly.” 

Dr Workman and Hayley-Jane Smith – who is herself from Birmingham – asked 48 volunteers one by one to look at photographs of four ordinary women.

As each photo appeared, volunteers would hear a script read out in a Birmingham or Yorkshire accent or the Queen’s English, or silence. The photos appearing with each accent were rotated between each volunteer to ensure looks did not affect the outcome of the study. 

The team from Bath Spa University found that the Yorkshire accent was considered most intelligent, followed by the Queen’s English, then silence and finally Brummie.

Perhaps partly to blame is the character of Brummie odd-job man Benny from Crossroads, played by actor Paul Henry. 

But comedian Jasper Carrott and actress Julie Walters, both of whom are from Birmingham, are certainly no dummies. 

Cricketer Darren Gough, writer Alan Bennett and chat-show host Michael Parkinson – all Yorkshiremen – are shining examples of the intelligence attributed to those with their accents.

Previous studies have suggested that the Birmingham accent is the most disliked in Britain. 

Experts believe this is due to British social snobbery, as visitors from overseas find Brummie “lilting and melodious”.

But Dr Workman, who presented his findings to the British Psycho-logical Society conference in Dublin yesterday, said regional dialects are becoming more acceptable. 

He said the fact that Received Pronunciation was no longer seen as the most intelligent-sounding was due to the growing number of youngsters from all backgrounds going on to higher education.

But his findings outraged Birmingham academics yesterday.

Dr Carl Chinn, professor of community history at the University of Birmingham, called the stereotype “infantile, puerile and prejudiced”.

“These surveys are seen as light and fluffy but they are not,” he said. “They have a deeply malevolent effect and stop people investing in the area that means there are not enough jobs. 

These surveys just create self-fulfilling prophecies.”

He said that despite more regional accents being heard on television and radio, most of these were “standardised” to make them more “acceptable”. 

He said that only when newsreaders had strong regional accents would the problem be solved.