BBC News, Cairo
Sheikh Tantawi insists he did not recognise Shimon Peres
Egypt's top Muslim cleric is under pressure to resign from politicians and newspapers for shaking the hand of Israeli President Shimon Peres.
Criticism has been steadily growing since the newspapers began running a photograph of the Sheikh Mohammad Sayyid Tantawi greeting Mr Peres.
The two met at the United Nations sponsored interfaith conference in New York in November.
Egypt and Jordan are the only Arab states to have made peace with Israel.
But the bitter reaction to Sheikh Tantawi's greeting of Mr Peres showed just how deep the resentment felt by many in Egypt towards its neighbour goes.
Sheikh Tantawi heads Cairo's al-Azhar University, Sunni Islam's leading religious authority and one of the oldest universities in the world.
He says the meeting was in passing, insisting that he didn't recognise the Israeli president. But his explanation has done little to deflect the criticism.
Among others, the leading independent newspaper al-Dustour, has been running a daily campaign calling for his dismissal.
The newspaper said Shimon Peres, whose career in Israeli politics has spanned 60 years, is tainted with the blood of thousands of Palestinians and that Sheikh Tantawi should richly purify his hands.
A spokesman for al-Azhar blamed Sheikh Tantawi's handlers for not paying closer attention and misdirecting him.
But the Israeli media has poured scorn on that version of the story.
The newspaper Maarif reported that it was Sheikh Tantawi that approached the Israeli president.
Although Shimon Peres has declined to comment on the row, his office said at the time the encounter was pleasant and that during dinner the two men had a very serious conversation.
Senior Egyptian politicians regularly meet with Shimon Peres.
Egyptian President Hosni Mubarak played host to the Israeli president just two months ago.
But Sheikh Tantawi, say commentators, is the leader of Sunni Islam and by shaking the hand of the Israeli president, he's seen as normalising relations with Israel while at the same time associating himself with the Egyptian regime, which is deeply unpopular in many quarters.