A body representing small businesses around the state released a report Monday slamming an insurance industry-led group's proposal to raise workers' comp rates by nearly one-third, calling it at one point "amateurish at best and deliberately deceptive at worst."

In its report, the South Carolina Small Business Chamber of Commerce attempts to pick apart the National Council on Compensation Insurance's request for a 32.9 percent increase this year in the premiums businesses pay to cover themselves against on-the-job injuries. That increase likely would be the highest in any state nationwide.

If the state Department of Insurance approves the rate request, total statewide worker's comp premiums would shoot up by at least $130 million. Many fear such a surge will stifle growth and discourage investment.

Frank Knapp, the Small Business Chamber's executive director and author of the report, said NCCI's proposed rate increase is based on "potentially flawed and unverified data" and doesn't give "full weight" to coming changes aimed at making the state's workers' comp system work better.

The Small Business Chamber is one of three groups that have petitioned an administrative law court to challenge the Florida-based NCCI's request.

The Department of Consumer Affairs and state Chamber of Commerce are the other two. Both of those groups, however, say they will wait to make their case at a hearing likely to be held this fall.

NCCI acknowledged that a steep increase such as it is proposing "can be disconcerting," but said it would be counterproductive to enter into a war of words.

"Rather than question the motivation or professionalism of those who disagree with our analysis, we work ... to pursue the best course for maintaining a healthy workers' compensation market," it said in a prepared statement.

The brouhaha over workers' comp got ratcheted up a notch last week when Gov. Mark Sanford appointed 11 people from a cross-section of professions to sit on a new advisory committee tasked with rooting out problems and offering recommendations by the end of the year.

If rolled out, the rate increase would be the third double-digit increase in three years. The increases have raised concerns in a state that had long been one of the cheapest for workers' comp policies.

The NCCI calculates workers' comp rates on behalf of insurers in about 40 states and presents rate requests to insurance departments each year.

In South Carolina, the group boiled down the rising costs to three main criteria: medical costs outpacing other states, higher attorney involvement here than elsewhere and slow settlement of contested cases.

Knapp's report seeks to poke holes in NCCI's conclusions by showing what he says are clear disconnects between cause and effect.

For example, Knapp points out that NCCI's own data show that underwriting losses for insurers peaked in 2000, even though that was when lawyer involvement in workers' comp cases was at its lowest level in years.

Knapp also notes that statistics from the state's Workers' Compensation Commission show attorney involvement is much lower than NCCI's numbers.

In addition, his report points out that data from a number of insurance carriers is not included in NCCI's analysis. Among those missing is American International Group, the state's biggest underwriter of workers' comp policies.

The report will be the cornerstone of the Small Business Chamber's case, though Knapp said he plans on showing up with a lawyer and statistician.

He also said he'll take his cues from the consumer affairs department, which has negotiated successfully with NCCI to lower its rate requests in the past.

Hana Williamson, an attorney with consumer affairs, said that while Knapp is asking a lot of good questions, it is premature for her department to comment.

"We are now waiting for a response from NCCI to our requests for data. It could take several weeks," she said.

Consumer affairs will consult an outside actuary in preparing its case, she said.

The state Chamber of Commerce, meanwhile, said putting out a report or even getting an actuary now would be "putting the cart before the horse."

"NCCI has some very smart people over there and we need to hear them defend these numbers before. Only then can we make an informed decision," said Tim Timmons, who heads human resources for the chamber and was selected last week to sit on the governor's workers' comp committee. "After we listen to their answers we'll see if we agree or disagree. We need to be real methodical about this."