HOME Affairs Minister Brendan O'Connor has appealed against the court ruling that spared 88-year-old Charles Zentai from extradition to Hungary.

Mr O'Connor had agreed to the extradition of Mr Zentai for the alleged murder of a teenage Jew in wartime Hungary.

The appeal comes six months after the Perth pensioner's win in the Federal Court, which quashed Mr O'Connor's decision that Mr Zentai was eligible for extradition.

Documents lodged in the Federal Court yesterday call for the July decision to be overturned on grounds that the judge erred. The appeal comes after Mr O'Connor's office sought legal advice.

Mr Zentai's legal appeals against extradition have cost him about $200,000, his son has said.

The former warrant officer in the Hungarian army is accused of plucking Peter Balazs from a tram in Budapest in the last days of World War II, taking him to the Arena Utza barracks and participating in a brutal beating that led to the teenager's death.

Mr Zentai, a conscript, has consistently denied any involvement in Balazs's death since details of the claims against him were revealed in The Australian in 2005.

Last month, Mr Zentai revealed he had faced an anxious wait to know whether the commonwealth would appeal against his court victory: "I'm left up in the air because of the government stretching out the case so much, unable or unwilling to make a decision since the 2nd of July."

Mr Zentai has long claimed he left Nazi-occupied Budapest on November 7, 1944, the day before Balazs, 18, was snatched and killed.

Balazs had survived on false documents that concealed his Jewish identity.

theaustralian.com.au