The band are to celebrate their tenth anniversary in 2012 and were expected to complete a three-week tour of the UK as part of their reunion in the Spring.
However, Nicola Roberts has claimed that the band's plans have been put on hold, meaning she won't reform with Cheryl Cole, Nadine Coyle, Sarah Harding and Kimberley Walsh until at least late 2012.
"I'm excited about us coming back but it won't be for another year now," Roberts told The Mail On Sunday.
Sarah Harding's trip to rehab to receive treatment for depression and alcohol addiction has been suggested as a reason for the delay. Girls Aloud were previously reported have issued Harding with an ultimatum to resolve her issues if she wants to join the tour.
"I can't say if Sarah will want to join the tour," Roberts added.
A band spokesman said: "No official plans have been announced."
Coyle recently admitted that she is not friends with her Girls Aloud bandmates and sees them purely as work colleagues.
Watch Girls Aloud's video for 'Whole Lotta History' below: