Polygamist sect leader Warren Jeffs arrives at the Tom Green County Courthouse, Thursday in San Angelo, Texas or the start of his trial. Tony Gutierrez/Associated Press

A Texas judge says polygamist sect leader Warren Jeffs can represent himself during his sexual assault trial but she will not delay its start further.

Prosecutors say Jeffs' frequent switching of attorneys has been a delay tactic. He has had seven attorneys and on Thursday, the 55-year-old fired his latest defense team and asked District Judge Barbara Walther for permission to represent himself.

A jury was being sworn in Thursday and Jeffs will be arraigned. The prosecution and Jeffs asked to delay opening statements until Monday, but Walther has not yet ruled on that request.

Jeffs is the leader of the Fundamentalist Church of Jesus Christ of Latter Day Saints. He is charged with sexually assaulting two girls and, if convicted, could go to prison for life.

Jeffs, 55, addressed the court for about 25 minutes, telling Walther that he thought hard before deciding he'd be better off representing himself. He asked for time to find another attorney who could help him file legal briefs.

He repeatedly said he needed a "pure defense," and, although he wanted to represent himself, he asked that he be given some assistance because his ability to work and write in prison are limited.

"The condition of my present defense is such that I cannot use them. They, not having all needed understanding for my defense, which wants for representation by one who knows and understands the facts of these truths," he said.

The charges against Jeffs stem from an April 2008 police raid on a church compound known as Yearning For Zion outside the town of Eldorado, about 70 kilometres south of San Angelo.

Authorities who believed girls were being forced into polygamous marriages removed more than 400 children living at the compound, and TV images of women wearing frontier-style dresses and 19th century hairdos were shown across the country.

The original call to a Texas domestic abuse hotline that sparked the raid turned out to be a hoax — authorities suspect that a woman in her 30s living in Colorado made it.

Most of the children seized from the ranch have since been returned to their families, but the evidence collected during the raid proved enough to charge Jeffs and 11 other church men with crimes including sexual assault and bigamy.

So far, all seven who have gone to trial have been convicted, receiving sentences of six to 75 years in prison.