Silverchair has been forced to withdraw from the line-up as a result of a medical condition suffered by the group's front man, Daniel Johns.

The Gone South Festival will proceed as planned. Australian chart-toppers, Killing Heidi, and stand-out attraction of Big Day Out, 28 Days, have now been added to the Festival to perform alongside American rockers Incubus (who SOLD OUT their first Sydney concert at the Hordern Pavilion in record time - 47 minutes), Something for Kate, Grinspoon, Machine Gun Fellatio, Sonic Animation, and 8 Tasmanian acts.

"Daniel and the band are extremely disappointed that they are not going to be able to play at Gone South", said the group's manager, John Watson. "Silverchair has done over 400 gigs in the last seven years and this is the first one that they have ever had to postpone. They would like to sincerely apologise to their fans for this inconvenience. Daniel promises to try and make it up to everybody when the band performs in Hobart in the last week of June."

Silverchair will now perform at the Derwent Entertainment Centre on June 29. Gone South ticketholders will receive a special $10 discount on the ticket price. They will need to hold on to their tickets, and present them when Silverchair's tickets go on sale over the coming weeks.

Watson added that any Silverchair profits from this late June concert will be donated to local charities as a further gesture of goodwill.

Silverchair's concert postponement has been necessary because Daniel Johns is suffering from a viral infection in both his knees. The infection causes severe swelling in these joints and is extremely painful. The debilitating condition has worsened dramatically in recent days and has actually made it impossible for Daniel to walk or even stand unaided. The condition is neither permanent nor life-threatening but his doctors have demanded complete rest for at least two weeks to help him recover from this infection.

According to Gone South promoters, Charles Touber and Karen Henderson, Silverchair's withdrawal from Gone South is a disappointment, but music fans will still get value for their money with the largest production and the largest concert bill ever assembled in Tasmania.

"We wish Daniel all the best for a speedy and good recovery and look forward to seeing him and the rest of the band in June", said Charles Touber. "We're also extremely happy that Silverchair have generously offered a discounted show to all Gone South ticketholders", he added.

More details on the June Silverchair show and ticketing arrangements will be announced shortly.