The spiritual leader of the world's 77 million Anglicans sparked a political and religious storm last week when he said the introduction of some aspects of sharia law in Britain was unavoidable.

That provoked a string of critical tabloid headlines, with the best-selling Sun launching a campaign for him to quit. Williams has said he was not advocating parallel systems of law.

He said he was not endorsing the harsh punishments meted out in countries such as Saudi Arabia and Iran, where murderers and drug traffickers are publicly beheaded or hanged.

The archbishop, whose spokeswoman said he was not considering stepping down despite the barrage of criticism, will defend his position in his opening address to the general synod, the Church of England's parliament.

Critics within the synod, which meets twice a year, have urged the archbishop to step down and may try to force the issue of sharia law onto the agenda of its four-day meeting in London.

Williams was praised on Monday by Prime Minister Gordon Brown as "a man of integrity."

Brown's spokesman said he understood the difficulties Williams was going through, but he added: "The prime minister believes that British law should be based on British values and that there are no plans to change that and there is no plan to introduce sharia law and make English criminal or civil law in any way inferior to religious law."

Sharia, the body of Islamic religious law based primarily on the Koran, as well as the sayings and deeds of the Prophet Mohammad, has been attacked by many in the west over its treatment of women and punishments for adultery and apostasy.

The row feeds into a broader debate on integrating Britain's 1.8 million Muslims. This issue has assumed greater urgency after suicide bombings by British Muslims killed 52 people in London's transport system in July 2005.

While the storm gathered around Williams, several Muslim leaders have thanked him and called for a cooler examination of his proposals, without making clear how they would work.

"His recommendation is confined to the civil system of sharia law and that only in accordance with English law and agreeable to established notions of human rights," said Muhammad Abdul Bari, secretary general of the Muslim Council of Britain.