Cher has infuriated residents of Adelaide after he key to the Australian city was sold online.

''I'm upset 2 & trying 2get2 bottom! I think my office f***** up? (sic)''

The 'Believe' singer's key - which she was presented with at the 1990 Grand Prix - was purchased on auction website eBay for $96,000 and Steve Condous - who was mayor when Cher was given the precious item - believes the episode is ''pretty poor''.

He told The Advertiser: ''I think that's pretty poor. I would have thought that getting the key to a city like Adelaide would have had some value to her, but obviously it doesn't because she wouldn't have got rid of it.''

All proceeds from the sale are going to Cher's charitable foundation, but the singer has taken to twitter to reveal she is ''upset'' that the key ended up on eBay.

She tweeted: ''I'm upset 2 & trying 2get2 bottom! I think my office f***** up? (sic)''