Saleem Said, of Woodcroft Street, Rossendale, had earlier pleaded guilty to murdering Leanne Collopy, 25, at Preston Crown Court.
He also admitted a further count of arson with intent to endanger life.
The court had heard police were called around 10.45pm on Sunday, July 30, following reports of a fire at a property in Burnley Road.
Emergency services attended the address where Said, Ms Collopy and their two-year-old daughter Leila were rescued from the building.
All three were taken to local hospitals suffering from a number of serious injuries.
Sadly Ms Collopy died on August 3. A post-mortem examination showed she had died as a result of burns and multiple stab wounds.
Following investigation it was established Said and Ms Collopy had previously been in a relationship which had ended some months previously.
Around 10.30pm on July 30, Said, with the couple’s daughter, visited Ms Collopy’s address claiming their child wanted to see her.
However, once inside the address, Said attacked Ms Collopy (pictured below, right, with daughters Lola and Leila) before starting a fire in the kitchen area with fuel from a petrol canister.
Neighbours, alerted to screaming inside the house, went to the front door of the address and saw the fire, calling emergency services for help.
Two police officers arrived minutes later. With assistance from members of the public they forced entry to the burning house and rescued Said, Ms Collopy and their daughter.
Ms Collopy had suffered multiple injuries and was taken to Royal Blackburn Hospital for treatment, but sadly died four days later.
Her daughter was also taken to hospital for treatment having suffered serious burn injuries. She spent some weeks at the hospital before being released to the care of her maternal grandparents. She has suffered life-changing injuries and she continues to receive support.
Said remained in hospital until September. Following treatment he was interviewed by police and subsequently charged with murder, attempted murder and arson.
Following today’s hearing, Said was jailed for 30 years.
Det Chief Insp Gareth Willis, of Lancashire Police’s Force Major Investigation Team, said: “Saleem Said is a cruel and evil man who has shown no remorse for his actions.
“Our investigation revealed his plans to commit this offence started several weeks before and involved the purchase of items to enable him to carry it out.
“On Sunday, July 30, Leanne was enjoying an evening at her friend’s house when she was contacted by Said. He lured her back to her home address having concocted a story that their daughter needed her mum. She returned home and once Said got inside he viciously attacked her and set fire to the property.
“Leanne and her daughter suffered horrendous injuries. It is clear she tried everything possible to protect her daughter and get her to safety. I have no doubt Leanne’s brave actions that evening saved her daughter’s life.
“The scene which my colleagues and members of the public encountered was truly shocking and I must praise their bravery at the scene in helping those inside the address to safety.
“Furthermore, l must also thank the wider emergency services for their help in extremely traumatic and ultimately tragic circumstances.
“We welcome today’s verdict and I feel the sentence reflects the callous and cowardly attack committed by Said on two defenceless victims.
“Specially trained officers continue to support the family who have behaved with immense dignity following this senseless attack. I hope today’s outcome provides some small comfort to them.”