The former accountant of John Rigas, founder of US cable operator Adelphia Communications, has backed prosecutors' claims that he used company cash to supplement his income.

Christopher Thurner testified that from the mid-1990s, Rigas asked him to submit fictitious invoices to the cable firm and arrange for multimillion-dollar loans of company cash.

Rigas, his sons Timothy and Michael, and one-time Adelphia executive Michael Mulcahey stand accused of using the public company as a "personal piggybank". They are on trial in a Manhattan court on charges of fraud and conspiracy.

Thurner testified that during the mid-1990s, Rigas senior asked him to charge Adelphia rent for guests staying at the family's apartments in Colorado and Mexico, when in fact the properties were empty at the time.

The first time Rigas made this request, Thurner says he refused, at which point the Adelphia boss allegedly threatened him with the sack.

Then in 1997, the testimony continued, Timothy Rigas -- the cable firm's chief financial officer at the time -- organised a line of credit for his father at the family's Highland Holdings business. When the elder Rigas required cash, it is claimed that funds were transferred from Adelphia to Highland, then sent to his personal account.

According to Thurner, the cable mogul withdrew around $50 million (€41.0m; £27.4m) from Adelphia via Highland between 1997 and 2002.

Data sourced from: The Wall Street Journal Online; additional content by WARC staff