Paul Crouch, 77, and his wife Jan Crouch, 73, run the Trinity Broadcasting Network which delivers the Christian message to every continent except Antarctica 24 hours a day, seven days a week. It bills itself as "the world's largest religious network and America's most watched faith channel".

The network broadcasts prosperity gospel programming, which promises that believers will be materially rewarded, and raked in $92 million in donations in 2010.

During a recent Praise-A-Thon one preacher asked viewers to shout "Fear not" three times, count down from 10, and then rush to the phone with donations.

The couple's granddaughter Brittany Koper, 26, has now filed court papers claiming she was sacked after discovering "illegal financial schemes" adding up to tens of millions of dollars.

Mrs Koper claims she was made to turn over her house, life insurance policy, car, furniture and jewellery to the organisation as "an act of Christian contrition" when she complained about alleged financial misdeeds.

A legal claim from another relative, Joseph McVeigh, alleged that TBN obtained a $50 million Global Express luxury jet through a "sham loan", owned an $8 million Hawker jet for Jan Crouch's personal use, and had 13 homes for the Crouch family's use across the United States. He claimed a $100,000 recreational vehicle was for the use of Jan Crouch's dogs.

The legal claims are offering a rare window into the secretive world of the sprawling religious empire, which the Crouches founded in 1973 with fellow televangelists Jim and Tammy Faye Bakker. The Bakkers left two years later to start their own ministry.

TBN shows Christian-themed news, documentaries, films, talk shows and sermons. It owns seven other television networks and has more than 18,000 television and cable affiliates.

In addition to its headquarters in Orange County, California, it has an estate outside Nashville called Trinity Music City USA, and a Christian amusement park in Florida called Holy Land Experience.

Last year Mrs Koper's father, Paul Crouch Jr, resigned abruptly as vice president of the network. Mrs Koper took over as chief financial officer in July.

She claims to have found that directors, members of her own family, were acting illegally. She sent a memo to the board but was sacked within days, according to her lawyer Tymothy MacLeod.

Mrs Koper claims her husband, also a TBN official, was sued by a debt collection company which had been registered by a TBN lawyer one day earlier. He was accused of embezzling $1 million from TBN, an accusation Mrs Koper claims was retaliation for her whistleblowing. The suit was dismissed.

Colby M May, a lawyer for TBN, rejected suggestions of family turmoil and financial wrongdoing. He claimed Mrs Koper and her husband had stolen from the network and that the legal claims were a "tabloid filing" and "utterly and completely contrived".

He said: "They're attempting to create a diversion and to create as much public spectacle as they can in the vain hope that this will all get resolved, and that's simply not going to happen."

He said the Crouches travel by private jet because they have received "scores of death threats, more than the president of the United States."

Their ministry keeps large amounts of cash in reserve because incurring debt goes against the Biblical instruction to "owe no man anything," he said.

He added: "The answer is, there is no fire there. They pay as they go and, every now and then, one of the things that they pay as they go on is the acquisition of a broadcast facility, and that's a multi-million dollar transaction."

Lavish Spending Of America's First Family Of Televangelism Revealed In Bitter Legal Feud