Attorney General Jeremy Wright has failed to persuade Court of Appeal judges to hand a harsher sentence to a man convicted of murdering his girlfriend's two-year-old son.
Craig Smith, 29, of Orton, Merseyside, was last year found guilty of murdering toddler Teddy Tilston, causing actual bodily harm to Teddy's twin sister Cassidy, and being cruel to both children, following a trial at Liverpool Crown Court.
Trial judge Mr Justice Garnham in November imposed a mandatory life sentence and ruled that Smith must spend at least 17 years in jail before being considered for parole.
Lawyers representing Mr Wright on Thursday argued, at a Court of Appeal hearing in London, that the minimum term should have been longer.
But three appeal judges disagreed.
Lord Chief Justice Lord Burnett, who headed the panel of appeal judges, said the minimum term imposed by Mr Justice Garnham was "appropriate" and
not "unduly lenient".
Smith was not at the hearing but watched proceedings via a video link.
Jurors were told how Teddy had been found unresponsive by paramedics in March.
They heard that the little boy's death had been caused by a tear to the wall of the abdomen.
Tests showed that he also had a bleed on the brain, likely to have been caused a week before his death, and bruises to his head, ear, upper lip, neck, jaw, abdomen and back.
Mr Justice Garnham said Smith had flown into a rage.
"I cannot say whether you punched him or kicked him or used your knee on him but I'm quite certain that you struck him in the gut with such force to cause that internal bleeding," Mr Justice Garnham had told Smith when passing sentence.
"I cannot speculate what might have caused that loss of temper but something, probably something trivial ... caused you to fly into a rage."