Austrian prosecutors in the trial of right-wing British historian David Irving filed an appeal Tuesday to contest his three-year prison sentence, saying it was too lenient. "The public prosecutor believes the ruling was too lenient in light of a possible sentence of up to 10 years and Irving's special importance to right-wing radicals," said Walter Geyer, spokesman for the public prosecutor's office in the Austrian capital Vienna. Irving on Monday pleaded guilty to denying the Holocaust, a crime in Austria. During the daylong trial, he insisted he had a change of heart and that he now acknowledged the Nazis' World War II slaughter of 6 million Jews. Irving also acknowledged he had erred in contending there were no gas chambers at the Auschwitz concentration camp. "I made a mistake when I said there were no gas chambers at Auschwitz," Irving testified, at one point expressing sorrow "for all the innocent people who died during the Second World War." On Wednesday, the self-educated historian gave an interview to UK-based Sky News, maintaining his story of a change of heart while still asserting that his previous expressions were legitimate, asserting that freedom of speech also involved the "right to be wrong". "I come from a free country and I'm not going to let anybody silence me," Irving said. The writer told Sky News that he was not a Holocaust denier, but acknowledged that his views had changed. "Any sane historian is going to be entitled to open this package that the media describe as the Holocaust and look at the individual contents and say 'well, this part I believe and this part I believe and most of that I believe but there is one thing here I don't believe. And that is what I did," he continued. "That is not denying the Holocaust. It is saying 'listen, I'm not a mug, I want to be told the truth and nothing but the truth,'" he added. "It is not so much of a change of heart, it is just a refining of your position." Irving's lawyer, Elmar Kresbach, said after the verdict was announced late Monday that he would appeal the ruling. He has already done so, according to the Austria Press Agency. Kresbach was not immediately available for comment Tuesday afternoon. Kresbach also told reporters that Irving would likely not serve the full three-year term because of various factors, including his age. Irving is the author of nearly 30 books, including "Hitler's War," which challenges the extent of the Holocaust, and has contended most of those who died at concentration camps such as Auschwitz succumbed to diseases such as typhus rather than execution.