In a letter to the U.S. Securities and Exchange Commission dated September 17, Nasdaq said the proposed compensation pool "goes well beyond what is required under current Nasdaq rules." It noted that if the proposal is not approved, the applicable limit of liability under the approved rule would instead be $500,000 - less than 1 percent of the proposed pool.

Major market makers and broker dealers say they lost upward of $500 million because of technical glitches during Facebook's May 18 stock market debut. Nasdaq's plan to offer $62 million in cash to compensate those who lost money was an increase from earlier discussions, which would have included a $40 million payback fund, made up mostly of trading rebates.

The proposal prompted a series of letters to the SEC in late August from concerned market makers, brokers, a trade group and lawyers who criticized Nasdaq's plan. Many called for changes or the outright rejection of the plan.

UBS Securities, an arm of the Swiss bank, said it lost more than $350 million in the botched IPO, and called the plan "woefully inadequate" in a letter to the SEC dated August 22.

The firm said the types of claims for trading losses that Nasdaq agreed to compensate "should be expanded to include the full extent of losses caused by Nasdaq." UBS said technical malfunctions from the IPO caused its systems to re-enter orders multiple times and left it with a huge position of unwanted stock.

Citi expressed similar discontent in its own scathing letter to the SEC in August in which it said Nasdaq's actions on the day of the IPO amounted to "gross negligence." The No. 3 U.S. bank's market-making arm, Automated Trading Desk, is said to have lost around $20 million in the IPO.

Both UBS and Citi declined to comment.

Nasdaq defended its use of a 45-minute window to determine a benchmark reference price to assess the amount owed on orders qualifying for accommodation after some market participants argued that the amount should take into account trading beyond the release of cross transaction reports at 1:50 p.m. that day.

The exchange said the timeframe "should have been ample time for a reasonably diligent member to identify any unexpected losses or unanticipated positions and take steps to mitigate or liquidate them."

Nasdaq said the purpose of the proposal is not to compensate all losses incurred on May 18 from Facebook's botched IPO, but to modify the $500,000 liability limit in order to make additional funds available for compensation in certain categories of loss outlined in its proposal.

The eight-page letter was signed by Nasdaq Senior Vice President and Corporate Secretary Joan Conley.

(Reporting by Ashley Lau in New York; Editing by Richard Chang and Dan Grebler)

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