The six-year-old accidentally set fire to the curtains while his mum went shopping, a court heard.
She'd left him on his own because she said he had 'been naughty'.
The tearful 26-year-old appeared at Leeds Magistrates' Court to admit child neglect following the fire last month.
Prosecutor Mike Vittis told the court: "The child set fire to the curtains in his own bedroom, causing them to fall on to his bed and set it on fire.
"Smoke billowed out from the windows which alerted neighbours.
"The child managed to get to the kitchen window and put his head out. The front door was locked at the time."
Neighbours called the fire brigade, who rescued the boy before putting out the fire, the court heard.
Mr Vittis added: "There he made comments to the police that he had been naughty on that morning, which was why he had been left at home."
The boy's mother was arrested by police, who determined that the child had been left alone for approximately 45 minutes.
The top of a lighter was also found in the middle of the child's bed. Ruth Bundey, mitigating, said the boy's mother had never left her son in this way before.
The case was adjourned for sentencing at Leeds Crown Court next month.
Neither mother or son can be identified for legal reasons.
More on Parentdish: Do you leave your children home alone?
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