Unionist politicians have accused gay rights campaigner Peter Tatchell of setting out to antagonise by giving a lecture in Belfast in which he will suggest that some historians believe William of Orange may have had male lovers.

Mr Tatchell has highlighted the controversial hypothesis as evidence of hypocrisy over homosexuality in Northern Ireland, but he was condemned by Unionists who claimed he will deliberately cause offence by delivering the Amnesty International Pride Lecture in Belfast tonight.

Mr Tatchell's appearance at the city's week-long gay pride festival comes after senior Democratic Unionist Party (DUP) politician Iris Robinson said that she believed homosexuality to be an abomination. However, Mrs Robinson, wife of Northern Ireland First Minister Peter Robinson, has also condemned all attacks on the gay community.

Mr Tatchell said: “It is particularly hypocritical for Unionist politicians to play the homophobic card when their hero, William of Orange, had male lovers.” He cited allegations that King William - loyalism's revered victor of the Battle of the Boyne in 1690 - had sexual relationships with men.

King William was married, but some academics have raised hackles by pointing to his promotion of young men to high office as evidence of bisexuality.

A DUP spokesman accused Mr Tatchell of setting out to antagonise. “This is the kind of deliberately offensive and provocative comment and shock tactics that he has used in the past,” he said.

Mrs Robinson sparked controversy when she said that in line with her Christian beliefs she sees homosexuality as an abomination. The DUP representative has also distanced herself from a House of Commons transcript that saw her suggest gay sex was more vile than child abuse - a comment she has said does not reflect her views.

The Strangford MP has repeatedly denied that her remarks were homophobic, insisting she had Christian love for gay people themselves and condemned anyone who would attack people for their sexuality. And when her husband was elected First Minister at Stormont, he used his acceptance speech to insist he and his party was committed to ensuring equality for all and defending the rights of minorities.

Mr Tatchell targeted Mrs Robinson for heavy criticism ahead of his Belfast speech. “Iris Robinson's remarks are part of a pattern of homophobia that seems to characterise sections of Northern Irish society,” said the Australian-born 56-year-old.

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