Chelsea Manning, the US army soldier serving a 35-year military prison sentence for leaking official secrets, has been threatened with indefinite solitary confinement for having an expired tube of toothpaste in her cell and being found in possession of the Caitlyn Jenner Vanity Fair issue, according to her lawyers and supporters.

Manning, a Guardian columnist who writes about global affairs, intelligence issues and transgender rights from prison in the brig of Fort Leavenworth, Kansas, has allegedly been charged with four violations of custody rules that her lawyers have denounced as absurd and a form of harassment. The army private is reportedly accused of having showed "disrespect"; of having displayed "disorderly conduct" by sweeping food onto the floor during dinner chow; of having kept "prohibited property" – that is books and magazines - in her cell; and of having committing "medicine misuse", referring to the tube of toothpaste, according to Manning's supporters.

The maximum punishment for such offences is an indeterminate amount of time in a solitary confinement cell.