The study comprises a screening phase up to 28 days, followed by a double-blind treatment phase of 12 to 48 weeks wherein subjects will receive a single treatment of either GSK1358820 100 U injection or Placebo injection, in a ratio of 1:1, with further stratification within the treatment arms according to the number of urinary urge incontinence episodes during screening. Subjects meeting the criteria for re-treatment will receive a second and third treatment. Each re-treatment will be with open-label GSK1358820 100 U injection, and will be spaced at least 12 weeks from the previous treatment.