The Trinity Broadcasting Network, which bills itself as the world’s largest Christian network, is embroiled in a legal battle involving allegations of massive financial fraud and lavish spending, including the purchase of a $100,000 motor home for family dogs.

Brittany Koper, a former high-ranking TBN official and the granddaughter of its co-founder, Paul Crouch Sr., was fired by the network in September after discovering “illegal financial schemes” amounting to tens of millions of dollars, according to a lawsuit filed in Orange County Superior Court.

“She blew the whistle and got terminated,” said attorney Tymothy MacLeod, who filed the suit on behalf of Joseph McVeigh, the uncle of Koper’s husband, Michael Koper, who was himself a high-ranking TBN officer.

“Brittany has done the right thing. It’s admirable that someone on the inside of TBN has come forward and is revealing to the world exactly what is going on behind those closed doors,” MacLeod said. “No good deed goes unpunished at TBN.”

The legal battle offers a rare glimpse into the private affairs of TBN, which is headquartered in an opulent compound near South Coast Plaza in Costa Mesa.

In his suit, McVeigh alleges that TBN maliciously sued him last year in an attempt to retaliate against Brittany Koper.

McVeigh’s lawsuit alleges that Brittany Koper was promoted to the position of TBN’s finance director in July because the network directors needed someone “within the family” to keep its financial “skeletons” hidden.

The lawsuit alleges that Paul Crouch Sr. obtained a $50-million Global Express luxury jet for his personal use through a “sham loan,” and that TBN funds paid for a $100,000 motor home for dogs owned by his wife, Janice Crouch, a network director.

The suit also alleges that TBN bought residences across the country for its directors under the pretext that they were “guest homes” or “church parsonages.” The properties include mansions used by the Crouch family in Newport Beach; side-by-side mansions in Windermere, Fla.; and homes in Nashville; Miami; and Irving, Texas, according to the suit.

TBN directors received about $300,000 to $500,000 in meal expenses and the use of chauffeurs, and oversaw “fraudulent donation and kickback schemes involving third party ‘ministries’” the network controlled, the suit claims.

The directors also misused funds to cover up sexual scandals, the suit claims.

The suit alleges that Brittany Koper refused to lie for TBN in a lawsuit brought against the network by a former employee, Horst Brandt, who claimed he was fired over age discrimination.

MacLeod said Brittany Koper was fired by Matthew Crouch, son of Paul Crouch Sr., after she submitted a memo to his father detailing her concerns about financial improprieties.

Network lawyers, for their part, said in a lawsuit last year that the Kopers used forged documents to embezzle funds to buy trucks, jewelry, a fishing boat, a motorcycle, a Lexus and life insurance, and gave McVeigh thousands of dollars without authorization.

MacLeod said the courts dismissed the lawsuit against the Kopers and McVeigh.

Requests for comment to TBN were referred to attorney Colby May, who could not be reached.

MacLeod said Brittany Koper plans to file a wrongful-termination suit against TBN.

TBN has been the subject of controversy before.

In 2010, the network settled a suit on confidential terms with a broadcast engineer who claimed he was discriminated against because he was gay. In another case, the network paid a $425,000 settlement to a former employee who said he had a homosexual encounter with Paul Crouch Sr., who denied the accusation.

Network preachers have been aggressive advocates of the “prosperity gospel,” the belief that God will bestow financial rewards on donors who give generously.

christopher.goffard@latimes.com