A Queensland mother has been sentenced to life behind bars for the gassing murders of her two children and the attempted murder of her teenage son.

The woman, who cannot be named, was found guilty in the Brisbane Supreme Court on Friday night of two counts of murder and one count of attempted murder after jurors deliberated on the case for six hours.

This afternoon she sobbed as Justice Philip McMurdo described her actions as “horrible”.

“The prime motivation was to avenge what you regarded as the wrong done to you by your ex-husband, the children’s father,” he said.

“On no rational view could this begin to justify an attack on the children, let alone the killing of them.”

She will not be eligible for parole until she has served 20 years.

At the time of the killings she had been angry that her ex-husband had won a Family Court order to have the children for the first half of the 2002-2003 school holidays, which included Christmas.