THE Gillard government has gone to the nation's highest court for clarity on whether accused war criminal Charles Zentai can be extradited to Hungary, six years on from the Perth pensioner's arrest.

The appeal to the High Court comes as Mr Zentai's Catholic priest attacked the government's handling of the case in a scathing letter to Julia Gillard.

Father John Flynn compared Mr Zentai's treatment to that of the 14-year-old boy facing drug charges in Bali who, he said, had received swift and extensive support from the government. In comparison, the government had offered no support to Mr Zentai and instead relentlessly pursued the extradition request, he said.

"One could be excused from coming to the conclusion that the Federal Government is much more willing to offer support to someone involved in a criminal act and incarcerated in an overseas prison than it is to support a good, law-abiding Australian citizen," Mr Flynn said.

Mr Zentai - a former warrant officer in the Hungarian army - is accused of plucking teenage Jew Peter Balazs from a tram in Budapest in the last days of World War II and participating in a brutal bashing that led to his death.

Hungary is seeking his extradition to face war crimes charges but in the latest legal decision on the case, the full bench of the Federal Court ordered the government to determine what constitutes a war crime under the extradition act between Australia and Hungary and whether Mr Zentai is allowed to be surrendered for such a crime.

The government wants legal clarity on the act and will not decide the issue for itself. Instead it sought leave to appeal to the High Court in documents lodged last week.

Father Flynn said if the government won in the High Court and Mr Zentai were extradited, "it will have contributed to major evils".

"It will have contributed to a major injustice, the forcing of a good law-abiding Australian citizen to leave his country without any account being taken of his side of the whole saga," Father Flynn said in his letter to the Prime Minister.

Earlier this month, Mr Zentai turned 90. His son Ernie Steiner said his father had a mini-stroke two days before his birthday and was "flat" about the latest legal development.

theaustralian.com.au