Guitarist Cox (far right) was taken to hospital on 9 June
The Long Blondes have had to pull out of Glastonbury and all of their forthcoming shows after their guitarist was taken seriously ill.
According to a statement on the band's website, guitarist Dorian Cox was taken to a Sheffield hospital on 9 June and remains in "a serious condition".
"We will regrettably be cancelling all our live appearances until the end of July," the statement said.
The band had also been due to support Duran Duran on their UK tour.
"Dorian is improving slowly and we will keep you updated on his condition," the band statement continued.
"If you would like to leave a message on MySpace, Facebook, or through the website, we would be glad to pass them on to him when we visit."
List of cancelled dates:
21 June - One Love Festival - Istanbul, Turkey
29 June - Glastonbury Festival, John Peel stage
3 July - O2 Arena, London (with Duran Duran)
5 July - Pop Circus - Milan, Italy
7 July - Birmingham NIA (with Duran Duran)
18 July - Summercase - Barcelona, Spain
19 July - Summercase - Madrid, Spain