Some of Iran's most senior politicians yesterday publicly challenged supreme leader Ayatollah Ali Khamenei by boycotting the ceremony in which he endorsed Mahmoud Ahmadi-Nejad as president.

In an embarrassing snub, former presidents Akbar Hashemi-Rafsanjani, a conservative, and Mohammad Khatami, a reformist, refused to attend the meeting as part of their efforts to deprive the next government of legitimacy.

The disputed re-election of Mr Ahmadi-Nejad on June 12 sparked the worst unrest in the history of the Islamic republic and highlighted a political split inside the regime.

Traditionally a former president would hand "credentials" - essentially a statement from the supreme leader - to the new president. But Mr Khatami, president for eight years between 1997 and 2005, refused to be involved.

Hassan Khomeini, the grandson of the founder of the Islamic revolution, and opposition leader Mir-Hossein Moussavi, who claims the election was stolen from him, were also absent.

The boycott indicates the extent of the rift within the Islamic regime.

Mr Ahmadi-Nejad was seen on state television kissing the shoulder of Ayatollah Khamenei, an act of respect not performed at previous ceremonies of this kind. It followed the president's unprecedented defiance of an order by Ayatollah Khamenei to remove his newly-appointed first vice-president. Mr Ahmadi-Nejad was forced to reverse the appointment after some fundamentalists warned that they could withdraw support for his government if he continued to disobey the supreme leader.