The lead singer of Florence + The Machine has suffered a ''vocal injury'' after she felt something ''snap''.
She apologised to fans for the cancellation of the shows in Spain and Portugal.
The redheaded star said: ''I've sustained a vocal injury and been told I cannot sing for a week - seriously I felt something snap, it was very frightening.
''Unfortunately this means I will not be able to perform at Benicassim and Optimus Alive festival this weekend.
''I'm so sorry to all the fans, I was desperate to still perform, but was told without question not to, so as not to do permanent damage.''
Her vocal problem comes less than a year after fellow chart star Adele was forced to cancel a number of shows and then had to undergo surgery after a vocal cord haemorrhage.
Welch is in line to top the singles chart with Spectrum (Call My Name) on Sunday according to midweek figures from the Official Charts Company.