Construction projects in and around the city centre are also being blamed for the decline.

Some traders said shoppers hoped to avoid the jams by going to Burton-upon-Trent rather than the city.

Jeweller Judith Hart, of Derby Chamber of Commerce, said trade was down at least 10% on last year but businesses were hoping to "ride out" the problem.

She said many shoppers thought there were fewer shops available at the Eagle Centre because of hoardings around the new Westfield development while traffic problems were also a deterrent.

Traffic lights

"It's difficult to get into Derby, they're adding more lanes, they're adding more traffic lights," she said.

"Eventually this will streamline traffic flow and it will help when Westfield is fully open next year.

"In the meantime we're making the best of it. For our customers we're still trying to make it a good experience - we're very positive for the future but this year has been tough."

Mike Matthews, also of Derby Chamber of Commerce, said the last few weeks had been difficult for businesses.

"I know people are going to Burton instead," he said.

"I hear people talk about going to shop in Burton - easier to get into, easier to find parking, albeit yesterday I went there on business and found it extremely difficult to park.