A South African court has dismissed an attempt by Oscar Pistorius' lawyers to stop an appeal that could see the athlete spend significantly more time behind bars for killing his girlfriend.

At the South Gauteng High Court in Johannesburg, Pistorius' defence tried to block the state's appeal against the champion sprinter being found not guilty of murder.

But Judge Thokozile Masipa, who presided over Pistorius' trial, criticised the athlete's lawyers and rejected their application.

The 28-year-old Olympian and Paralympian athlete was last year found guilty of culpable homicide, a charge akin to manslaughter, and sentenced to five years in prison for shooting Reeva Steenkamp on Valentine's Day 2013.

State prosecutors were granted permission in December to appeal against the verdict, arguing that Judge Masipa misinterpreted the law when she ruled Pistorius did not intentionally kill Ms Steenkamp when he shot four times at a locked toilet door.

Pistorius' legal team countered that his conviction was based on facts presented during the trial and therefore could not be appealed.

The judge this morning said Pistorius' lawyers should argue their point in the appeals court itself, adding there was "nothing new" in their application.

"Before I gave my finding in December, both counsel had an opportunity to argue whether the points raised at the time were points of fact or points of law," Judge Masipa told the court.

"Procedurally it would be wrong to grant or refuse this application... I strike off the application."

Judge Masipa's decision paves the way for the prosecution's appeal to go ahead.

During the trial, Pistorius testified that he shot Ms Steenkamp believing she was an intruder, while the state argued he deliberately killed the 29-year-old law graduate and reality television star after an argument.

If an appeals court finds him guilty of murder, the athlete, known as the "Blade Runner" for the prosthetic legs he wears on the track, could face at least 15 years in jail.