AN Adelaide woman embroiled in Australia's most expensive divorce is suing her former lawyers, claiming their multi-million dollar legal bill is "unfair and unreasonable".

In documents filed with the Supreme Court, the woman - who cannot be named - claims she has paid $10.5 million in legal fees since her "extremely complex" divorce proceedings began in 2005.

She has asked the court to intervene in a $4.3 million bill, issued by one city law firm for its services. She says the firm's staff generated 23,000 documents and 480,000 computer files about her case - filling 182 archive boxes.

Her estranged husband, she claims, has spent $26 million for representation over the same period.

The woman has asked the court to review her bill and determine how much she should have been charged for the firm's work.

"Throughout the ongoing conduct of the (divorce) action I have become extremely concerned and stressed as to the amount of legal fees and disbursements I have incurred," she says in an affidavit filed by her new lawyers.

"I have exhausted nearly all my available funds and only have nominal funds to live on and (for) the day-to-day care of my son."

It is understood the woman is seeking a multi-million dollar property settlement, and millions in child support, from her husband.

In her affidavit, the woman admits her divorce has been "extremely complex".

She says that in December 2007, her then-lawyers wrote to her saying they "could not continue to act" unless she deposited $750,000 into their trust account.

She claims that in March 2008, she was told her outstanding legal fees totalled $650,000.

She says she terminated her dealings with the firm in April 2008 but, one month later, learnt it had $926,653.93 of her money in its trust account.

The woman says she needs the court's help due to "what appear to be discrepancies" in her account statements.

"I have repeatedly requested ... a final tax invoice for my consideration," she says.

"To date, I have not received a bill of costs in taxable form."

In its defence papers, the firm denies it has been unfair or unreasonable.

It says the woman was "fully informed" that "not all lawyers charged on the same basis".

It claims she wanted to "maximise the chance of a successful outcome" of her divorce. She was therefore charged for "the level of legal resources needed to conduct the matter thoroughly".

At a hearing last month, the firm asked the woman be ordered to disclose all correspondence she'd had with other lawyers.

Judge Robert Lunn refused the application.

"For many years, (the woman) has been involved in a mammoth and bitter divorce case," he said.

"Whether she has spent $10 million or $15 million is not the basis of the argument.

"It is, in colloquial terms, whether she has scraped the bottom of the barrel in pursuing her claim (and) this seems to be beyond argument.

"Hence, I do not consider she should be put to the time, trouble and expense of having to (disclose) all the documents ... for all the legal and related expenses she has incurred in this long and complex case."

The matter returns to court next week.