A leading Egyptian presidential candidate lashed out Monday at an Islamist lawmaker who accused him of graft, treating voters to a new spectacle in an already unprecedentedly heated campaign.

These are the first competitive presidential elections in the country's modern history, and in the last week of the campaign period the candidates are facing a level of public scrutiny rarely seen before in Egyptian politics _ including televised debates, interviews and legal challenges.

The front-runners include two former officials from the era of deposed president Hosni Mubarak and two Islamist candidates. They have clashed over the role of religion, the degree to which the country needs to change, and whether politicians from the old Egypt should hold office in the new.

The May 23-24 vote follows 29 years of Mubarak's autocratic rule. He was the sole candidate in all but one of the presidential contests in that period, and it would have been unthinkable for him to have to face such questions.

Mubarak was forced from power by a popular uprising in February 2011. A ruling military council took over and has promised to hand over power to a civilian president by June 30.

Official campaigning began two weeks ago. On Thursday, an Islamist candidate and a former foreign minister participated in the Arab world's first-ever public presidential debate, in which they traded accusations about each other's political history.

Now Ahmed Shafiq, a former air force pilot and Mubarak's last prime minister who is seen by some as the military's preferred candidate, is the latest contestant to have to answer for his record.

Islamist lawmaker Essam Soltan accused Shafiq of using his offices as a head of a air force pilots' association in the 1990s to sell a large plot of state land at a below-market price to Mubarak's sons.

Soltan raised the accusations in parliament and filed a complaint to the public prosecutor Sunday. The prosecutors are currently investigating the case.

Shafiq swiftly denied the accusations, saying it was part of a "defamation campaign" against him by the Islamist-dominated parliament.

This is not Shafiq's first brush with Egypt's new unpredictable political system. He was already briefly disqualified from the race after the Islamist-dominated parliament passed a law barring former top regime officials from the past 10 years from running for office. But he was reinstated 24 hours later after the presidential election commission referred the law to the Constitutional Court.

In his Monday press conference, Shafiq took a jab at the parliament and at Soltan personally, saying they were on a campaign to hinder his rise.

He said he wanted "to answer to these fabrications Soltan is throwing my way arbitrarily as part of an organized defamation campaign."

He threw out an accusation of his own, accusing Soltan of being a regime agent who spied on the protesters at the height of the uprising that brought Mubarak down. Shafiq also accused him of being used by security agencies to carry out sting operations against other Islamists, including the Muslim Brotherhood.

Islamist groups were Mubarak's best organized opponents and were the main target of his crackdowns.

"All he wished was to lick shoes to be allowed to form his own party," Shafiq said. "I wish that when someone acts like a man, he is a man all his life."

Soltan dismissed Shafiq's accusations as "unsubstantiated," mocking what he said was a transformation from a Mubarak loyalist to a champion of the opposition.

Both sides are playing to fears about their opponents: the Islamists suggesting that the former regime officials will take the country back to the days of Mubarak, and the former officials suggesting that the Islamist candidates will impose a hard-line religious agenda.

The powerful Muslim Brotherhood, which is also fielding a candidate, posted on its website Friday a religious edict, or fatwa, saying it was religiously banned to vote for the two former regime officials.

"Giving votes to people like these amounts to cooperation with them in aggression and wrongdoing, and failing the honest. ...We urge all Muslims_ all honorable Egyptians_ not to fall for this trap," the edict said.

Thirteen candidates are listed for the May 23-24 vote. If as expected no candidate takes a majority, a run-off between the top two will take place June 16-17, and a president is to be declared on June 21.