Malcolm Webster, 54, was jailed for a minimum of 30 years for killing Claire Morris, 32, in the planned smash in Aberdeenshire in 1994 and attempting to kill Felicity Drumm in New Zealand in 1999 to claim insurance money.
The former nurse, from Guildford, Surrey, was handed the life sentence after being convicted of the crimes in May 2011.
Judges at the Court of Appeal in Edinburgh today rejected a claim that he was the victim of a miscarriage of justice.
Webster's legal team argued that scientific experts, who gave evidence at the trial, had not been able to rule out the possibility that the fatal car fire started accidentally.
As a result there was insufficient evidence for the jury to conclude that Ms Morris had been murdered, they said.
But Lord Eassie, delivering the opinion of the three appeal judges, said: "There was nothing in their testimony offering any real, positive support for a contention that, given the interval before it erupted, this fire was accidental."
He said that the prosecution case that the fire was deliberate did not rely solely on expert evidence.
Lawyers for Webster attacked the decision of trial judge Lord Bannatyne to allow the Crown to call a late witness, farm worker Ian Hardie, who contacted prosecutors after the trial had begun.
Mr Hardie gave evidence that he had seen Webster at the site of the fatal crash 11 days before it occurred. Prosecutors argued that this was him familiarising himself with the spot before staging the crash.
Webster's lawyers said extensive media coverage of the trial had created prejudice which called Mr Hardie's identification into question.
But Lord Eassie said: "Mr Hardie's emergence as a potentially material witness came to all engaged in the trial as something wholly unexpected.
"The assessment of prejudice was a matter of assessment for the trial judge when he came to consider whether he should exercise his discretion to allow the additional evidence to be led. We have come to the view that his assessment is not open to successful challenge."
Webster's legal team also argued that the significant differences between the murder of Ms Morris and the attempted murder of Ms Drumm meant the two Appeal judgessaid this was "not well-founded".
A hearing on Webster's appeal against sentence will be held at a later date.