The judge added that Miss Chambers "carried not a shred of blame" for what happened.
"Instead of thinking of his daughter who he has claimed to love, he concentrated on himself alone and most particularly his desire for revenge and his determination that no other man was going to be Christine's partner or act as Shania's father," the judge added.
"He resolved that, if the family was at an end, that they would pay for leaving him with their lives and that their last hours of live would be terrifying and, in the case of Christine Chambers, extremely painful."
The judge said Oakes "planned the deaths in elaborate detail" and took with him a series of implements to inflict pain on Miss Chambers.
He made her beg and proclaim her love for him while at the same time "torturing" her, the judge added.
Miss Chambers' family wept as the judge said: "Shania would have witnessed her mother's gravely injured state and heard her cries for help. She would have seen the appalling injuries to her mother.
"That little girl must have been terrified. He then put the shotgun against her head and pulled the trigger.
"No decent, civilised human being could ever describe that as being the result of love."
Oakes did not appear in court to be sentenced.
Richard Connolly, in mitigation, said his client's absence for the verdict and sentencing was "not intended to show disrespect to the court, jury or the verdicts that have been passed".
He added prison guards had been concerned for Oakes's safety because he "expressed emotions" which made them fear he may harm himself.
Andrew Jackson, junior prosecution counsel, read an excerpt from a statement by Miss Chambers' family.
It said: "The tragic loss of Chrissie and Shania has deeply impacted on all of our everyday lives. No parents should have to outlive their child, let alone grandchild."
Miss Chambers' 10-year-old daughter with former partner Ian Flitt witnessed the attack but escaped out of the bedroom window to her father's house nearby.
Mr Jackson said the 10 year old - Shania's half-sister - had suffered from post-traumatic stress disorder ever since.
Oakes had some "old and trivial" previous convictions committed "within the context of his relationship with Christine Chambers", he added.
Chris McCann, head of the Crown Prosecution Service's East of England complex case unit, said outside court: "This was an extremely violent and horrifying assault by Oakes upon Miss Chambers in advance of a family court hearing over access to Shania and driven by a determination that he would kill both Christine and Shania before attempting to kill himself.
"Our thoughts are obviously with the family of Miss Chambers who behaved in such a dignified way throughout the trial."
