Lauren Booth was let off with a 12 month suspended sentence for wilfully ill-treating or neglecting son Aaron – and to onlookers' astonishment, she was seen smiling and laughing as she left court.
Judge Colin Burn told Booth that her son had died a prolonged and agonising death as chemicals burned his lips, tongue, oesophagus and stomach.
She had been lying in bed with her boyfriend at 12.45pm as 'hungry and thirsty' Aaron drank the plant food that he thought was his favourite drink.
Aaron's dad, Mohammed Khan, 33, from Huddersfield, said the sentence was 'disgusting'.
"Aaron's gone, he's not coming back," he said.
She's been found guilty of neglect and she hasn't been given a proper punishment. It's sickening.
"Where's the justice for Aaron? She's not been punished for taking my son. She's got her life but Aaron hasn't got his.
"I don't believe she's ever shown remorse. She cried in court but she wasn't crying for Aaron, she was crying because she didn't want to go to jail."
Bradford court was told Booth found her son with brown lips and struggling to breathe after he drank a 10ml dose of the poison. He died 11 days later in hospital.
Judge Burn said jobless Booth, 23, of Huddersfield, was guilty of a "cataclysmic, single failure".
He added: "Aaron was almost three, at an age where he was curious and everything was a challenge.
"By failing to supervise him you allowed this to happen.
Aaron's death was a horrible one. And it was preventable.
"By moving the plant food along the windowsill and forgetting about it and also by failing to get up in the morning to look after Aaron, knowing the bottle was in the house, you acted in neglect."
Michelle Colborne QC, mitigating, said Booth, who has a one-year-old child in foster care, has been attending parenting classes.
"She says she had to hit the bottom before appreciating what was required of her to have a proper decent life," said Ms Colborne.
"She will live with this for the rest of her life."
Judge Burn told Booth he was satisfied she did not pose a risk to her other child.
He said: "No one suggests you set out to harm Aaron. The unfortunate aspect is your poor judgment led to fatal consequences.
"I'm persuaded that you appreciate the real significance of your failure to act on this occasion.
"Therefore no further punishment is required to make this any clearer."