Britain's defense secretary and at least three lawmakers have pulled out of speaking engagements at the debating society at Oxford University after the group's president invited David Irving, the historian once jailed in Austria for denying the Holocaust, to speak. Defense Secretary Des Browne and the other officials decided not to speak at the Oxford Union after learning that Irving and the far-right British National Party Leader Nick Griffin had been invited to a forum on free speech. The Free Speech Forum is planned for November 26. Neither Browne nor the other lawmakers were invited to attend that event, but had been scheduled to speak on other days. Irving was arrested in November 2005 on charges stemming from two speeches he gave in Austria in 1989 in which he was accused of denying the Nazis' extermination of 6 million Jews. Denying the Holocaust is a crime in Austria, which was occupied by the Nazis. Irving has refused to use the term Holocaust, calling it a concept that "became cleverly marketed." Irving was convicted in February 2006 and sentenced to three years in prison. He served 13 months and was released on probation. Griffin runs a party that campaigns on a fiercely anti-immigration and anti-Muslim platform. An adviser to Browne, who spoke on condition of anonymity in line with government policy, said the defense chief believes the union has the right to invite Irving and Griffin. However, Browne did not find it appropriate to speak in the same place, the spokeswoman said. The union's president, Luke Tryl, wrote a letter to the society's members in which he said he invited the men to talk about the limits of free speech - not to expound their views. "Stopping them from speaking only allows them to become free speech martyrs... groups like BNP do well if they look like they're being censored," he wrote in the letter. Tryl did not respond to an e-mail and several telephone inquiries made by The Associated Press. More than 1,000 people have signed a petition on the 10 Downing St. Web site calling for Prime Minister Gordon Brown to condemn the invitations to Irving and Griffin, with the aim of persuading the group's president to revoke the invitations. Denis MacShane, a Labour Party lawmaker, withdrew from a speaking engagement at the union last week. "Inviting two notorious Jew-haters... to the most prestigious debating student forum in the world will validate today's anti-Semitism which is a poisonous ideology emanating from the extreme right as well as the Israel-hating left and Islamist ideologues," MacShane said in an e-mailed statement. "The British National Party mixes anti-Semitism and Islamaphobia in equal measure. David Irving is the Holocaust Denier-in-Chief."