Matthew John Davey was jailed for 18 years in 2021 for attempting to murder his then-20-year-old partner at a home in Hobart's northern suburbs in 2017.
Davey, who was found guilty by a jury, poured fuel on the woman in a shed and then lit it with a cigarette lighter after she told him their relationship was over.
The woman suffered catastrophic burns to 68 per cent of her body.
Davey, who admitted to persistent family violence, had previously threatened to kill the woman if she left him, monitored her and restricted her movements by damaging her car.
His appeal against the attempted murder conviction and jail sentence was dismissed by Tasmania's Supreme Court of Criminal Appeal on September 20.
Davey claimed he had "fresh" evidence from Brett Pickett who said he saw the woman pour petrol on herself during an argument with another woman at a property in a different suburb.
Pickett said he found out the next day the woman had been badly burned and Davey was "in jail for it".
Justice Tamara Jago said Pickett's evidence, provided in a written statement signed in September 2023, was not cogent or plausible.
She questioned why it took Pickett so long to provide his alleged evidence.
"I am in no doubt that his account is a fabrication directed at assisting (Davey)," Justice Jago said in a recently published decision.
"To put it bluntly, I found Mr Pickett's evidence inherently implausible and unbelievable."
Davey and Pickett were housed together in the same unit at Risdon Prison for 216 days between 2017 and 2023, Justice Jago noted.
Under cross-examination, Pickett said he and Davey knew each other in custody but were associates rather than friends.
Other grounds of Davey's appeal, including that his lawyer at the trial was incompetent, were also dismissed.
Sentencing judge Michael Brett said Davey showed "no remorse" and tried to cover up the crime.
"As you were waiting for emergency services ... you asked the (woman) to lie to others about how the fire had started," Justice Brett said.
"You told a number of emergency services personnel, police officers and a doctor that the fire had been caused by an accident."
Justice Brett said the woman gave a credible account of what happened.
Davey is serving 22 years' jail in total for attempted murder and persistent family violence and will be eligible for parole in 2033.
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