By Robert Evans

Reuters, Geneva

GENEVA, April 22 (Reuters) - Three key United Nations human rights investigators challenged on Wednesday the idea promoted by Islamic countries that "defamation of religion" is racism and should be internationally banned.

In a statement at the U.N.'s controversy-dogged Durban II conference on race and discrimination, they said the concept -- endorsed by big majorities in the world body for the past 10 years -- was, like related blasphemy laws, open to abuse.

"Whereas some have argued that 'defamation of religions' could be equated to racism, we would like to caution against confusion between a racist statement and an act of 'defamation of religion'," they declared.

"There are numerous examples of persecution of religious minorities or dissenters, but also of atheists and non-theists, as a result of legislation on religious offences ...," added the three -- from Kenya, Pakistan and Guatemala.

Islamic states backed by a range of allies had earlier sought, against fierce Western resistence, to have the "defamation" concept included in a declaration that was endorsed by consensus on Tuesday at the racism conference. They agreed to drop it in what U.N. High Commissioner for Human Rights Navi Pillay has hailed as a spirit of compromise, but in speeches to the conference they have continued to insist that action against it is vital.

Only last month they and allies including China, Cuba and Russia pushed through the latest resolution condemning defamation -- which critics argue is aimed at undermining free speech -- at the U.N.'s Geneva-based Human Rights Council.

The first such resolution was passed in the Council's predecessor, the Human Rights Commission, in 1999, and similar non-binding texts have been approved in the U.N. General Assembly in New York, the latest last December.

The three experts speaking on Wednesday were the Council's own special investigators for racism, Githu Muigai of Kenya, for freedom of religion and belief Asma Jahangir of Pakistan, and for freedom of expression Frank La Rue of Guatemala.

They read their statement -- taking turns with sections of the text -- at a U.N.-organised side-event during the racism gathering -- boycotted by the United States, Israel and seven other countries.

"The right to freedom of expression constitutes an essential aspect of the right to freedom of religion and belief ... essential to creating an environment in which a critical discussion about religion can be held," they said.

Muslim countries in the 57-member Organisation of the Islamic Conference OIC), argue that "defamation" of their religion -- in Western newspapers, television programmes and even academic studies -- violates believers' human rights. They say that it is linked to a wave of Islamophobia in Western countries since the attacks in the United States in September 2001, and was highlighted by cartoons in Danish and other European newspapers in 2005 and 2006.

However Pillay, who was echoed by the three experts, said on Tuesday she saw the conference declaration as showing a shift in the debate away from condemning "defamation" to ensuring that government acted to prevent "incitement to hatred".

Incitement to hatred and violence is already banned under existing U.N. pacts accepted by most members states, but human rights activists say governments around the world, including in Islamic countries, are not active enough against it.