A heartbroken family has hit out at a decision by the Attorney General not to increase the "soft sentence" of a van driver who killed two children.
Rhiannon Lucas, 25, from Tredegar, called for a change in the law following the deaths of her children, Gracie-Ann, four, and brother Jayden-Lee, three.
They were killed drink driver Martin Newman, 41, in February after his Ford Transit van struck the family's car on the M4.
He was sentenced to nine years and four months but will be released from prison on license in just over four years.
In response, Ms Lucas said: "His nine year sentence is completely inadequate and pathetic.
"He has killed two children. He should be serving a life sentence for what he has done, although no sentence will ever be enough.
"The law needs changing and sentences for crimes like this should be much, much tougher.
"I will not stop fighting for his sentence to be increased."
However the Attorney General's Office has said there will be no appeal under the 'Unduly Lenient Sentence scheme'.
The children's grandfather, Jason Lucas, said: "I'd like to see the man who said it's fair to come and say it to my face.
"He took two kids away from us. What we've had to go through, it's terrible. I wouldn't want that for anybody. It just ripped us apart."
The family had been returning from a birthday party when their car was hit by Newman, while he was drink and drug driving in his white Ford Transit van.
He swerved across three lanes of the M4 before hitting the family's red Ford Fiesta while it was stationary in the hard shoulder.
The legal scheme means members of the public can ask for sentencing to be examined within 28 days of it being handed down. The family had set up a petition calling for a tougher sentence and have received over 3,000 signatures.
The Attorney General's Office said the solicitor general was "shocked and deeply saddened" by the case.
"After careful consideration the solicitor general has concluded that this case cannot properly be referred to the Court of Appeal.
"A referral under the Unduly Lenient Sentence scheme to the Court of Appeal can only be made if a sentence is not just lenient but unduly so, such that the sentencing judge made a gross error or imposed a sentence outside the range of sentences reasonably available in the circumstances of the offence.
"The threshold is a high one, and the test was not met in this case."
During his case, the court heard how Newman had been drinking double vodka and lemonades with workmates the night before the crash.
He had been staying at a hotel near Leicester for work when went he back to his room and drank ten cans of Strongbow and took cocaine until 5am.
Father-of-two Newman attempted to go to work the following morning but was too "tired, drained and hungover."
He then decided to make the journey back to South Wales with a bottle of wine in his cup holder while he took sips for his "dry mouth."
It also emerged that witnesses had seen Newman "glued to his phone" behind the wheel as he was embroiled in a heated argument with his ex-partner.
Following the crash, emergency services found Newman crying with blood on his hands and smelling of alcohol.
Both children are said to have suffered catastrophic brain injuries in the crash while their mum Rhiannon suffered rib fractures and a torn liver.
Gracie-Ann died at 4.45am the following day. Her brother Jayden-Lee died five days later at the University of Wales Hospital in Cardiff.
Newman, of Croeserw, near Neath, pleaded guilty to causing their deaths by dangerous driving. He admitted to seriously injuring their mother by dangerous driving and by driving above the alcohol and drug limit.
Judge Daniel Williams said the maximum sentence was 14 years but Newman was entitled to a reduction for his early guilty plea.
Mr Justice Williams said: "Many think such a sentence is inadequate to reflect what you have done and there will be many who will call for that maximum sentence to be re-examined.
"That is not a matter for any court but Parliament."