A fibrous sheet having a basis weight of between 20 and 1000 g/m2 that disintegrates in water, has 10% to 70% starch on the basis of the total weight of the dry fibrous sheet. The disintegration time in water, measured in accordance with standard NF Q34-020 applied to a specimen of the sheet of 9×8 cm2, is less than 50 seconds. A loss of strength of the sheet measured in accordance with a defined table test corresponds to a loss of strength of a specimen of said sheet forming an angle of at least 85° after having being wetted with water for a duration of 6 seconds, and/or a residual wet strength of the sheet relative to its dry strength, as measured according to a defined ring crush test, is less than 1%. The fibrous sheet may be used for the manufacture of a water disintegrable core in a roll of tissue paper.